Document Oz518maOeZzNvBKdpz1yz7Gg1

I The Industrial Chemist, October, 1939 ; THESE MATERIALS PROVIDED BY BALL STATE UNIVERSITY LIBRARIES NOTICE: This material may be protected by Copyright Law (Title 17, US Code) Air-Borne Matter, Part Characteristics and Industrial Implications By Henry L. Muntgomery Larcombe I 379 THE centralisation of industrial activity' in and around the great cities of the -world has resulted in the pollu tion of the surrounding air by a great variety of air-borne (4) Condensation of Gases and Vapours. Formation of rain from water vapours. Condensation of metallic vapours. matter. This matter may range from heavy process dust (5) Chemical Reaction. Production of chemical smokes to smoke particles beyond human visibility. It may be a in industrial plants. direct product or an indirect product, but it is essentially (6) Various Natural Origins. Pollens, animal excreta, a nuisance. The direct importance of collecting dust fungi, soil, sand, bacteria and particles of dead that has commercial value is obvious. In addition, there insects. should be taken into consideration the indirect financial importance of eliminating or collecting all kinds of dust, fog, fume or smoke, to reduce building and equipment Measurement -of Particle Size maintenance, to increase human comfort and well-being, Particles of very small dimensions have a relatively large eliminate dangers of occupational disease and generally surface area as compared with their weight. Therefore, increase the efficiency of the industrial machine. when suspended in a gaseous medium they are carried The average impurity content of the atmosphere in freely by virtue of the viscosity of this medium. The country districts is less than 1 mg. of solid matter per consequent system is not in equilibrium, and is subject to cu. m. This increases in a city to an average of 3 mg. constant and numerous changes. The degree of instability per cu. m. and as much as 5 mg. in an industrial centre. is dependent on the properties and size of the particles, This has been confirmed by dust counts with apparatus the medium of suspension and the influence of external designed especially for this work. The number of particles forces such as gravitj', centrifugal force, convection counted in 1 cu. ft. of air varies, but the dust count is currents or magnetic force. basically dependent on the manner in which the dust Measurement of Particles.--These dispersoids may be of counter collects the particles on glass slides and upon the a solid or liquid nature. If they are liquid they may take degree of magnification. Dust determination made with on a spherical form. Solid particles, however, are not the Aitken dust counter in Glasgow found 3,736,000 usually round, their outline depending upon the structure particles per cu. in. In the United States experiments of the material of origin, and upon the process by which made with the Hill dust counter in a number of large cities they were generated. They are generally reproductions have resulted in an average of 9,700 particles per cu. ft.; of the original materials ; silicaceous particles assume the an average of 500,000 particles per cu. ft. was counted form of irregular broken stones ; wood dust has the during an investigation of the open atmosphere of New appearance of minute splinters. York City by means of the Owens jet apparatus. The unit of measurement of particle size is now almost Between the hours of 8 a.m. and 6 p.m. in winter months universally accepted to be the micron (1/1,000 mm.). For the average impurity content is in the region of 0-56 lb. this branch of science it is obvious that the microscope is per 10,000,000 cu. ft. of free atmosphere. In London it the chief instrument of size classification. The detection has risen to a peak content of 1 1 lb. per 10,000,000 cu. ft. of many ranges of dust -necessitates the use of polarised of free atmosphere. Air-borne matter is not confined to the free atmosphere. light. For a standard of comparison the diameter of the The dust hazards in factories and mines are of an extremely human hair varies from 60 to 150 microns, the average dangerous nature, and comprise the most important section so far as health is concerned. Any figures we may give for being in the region of 90 microns, and an object of 10 microns diameter is generally considered to be the absolute the free atmosphere are dwarfed by the dust content of limit of unaided human vision. Considering the above &>r in mines and factories where concentrations of anything remarks, it is not surprising that such a small unit of op to 400 mg. per cu. m. are experienced. measurement is required for this particular work. The field of study of dust technology is such a vast one nd touches so many schools of science, that all its branches Arithmetical Mean.--To indicate the size of such particles, the diameter is usually given. Only perfectly round cannot be covered in any single work. It is the purpose of this discussion to review the fundamental characteristics of air-borne matter which must be set down before any detailed research can be made on any particular branch. particles have an accurate diameter, and as has already been pointed out, solid particles have usually an irregular form. Therefore, for these particles another method of measurement is introduced; that is, the arithmetical mean, which is a single figure, and will be the equivalent Origins of Air-Borne Matter of the diameter in a spherical particle. This figure is the mean of length, width and height. In the case of particles Dust dispersoids or aerosols in the air are generally of which the length is considerably greater than the other assumed to be originated in the following manner :-- dimensions, which include fibres and other elongated (1) Combustion and Explosion. Reduction of solid shapes, a correction factor must be applied when the laws and liquid fuels to ashes, fumes and smoke. of settling have to be considered. (2) Crushing. Disintegration of concrete and asphalt, Surface Mean Diameter.--When studying dust in the process dust, milling, pulverised coal, etc. form of a very fine and fairly even powder, it is usually (3) Mechanical Dispersion of Liquids. Spray evapora more accurate and convenient to work with the surface tion, particles of salt in the atmosphere of mean diameter of the powder. This can be calculated : seaboard districts. after the arithmetical mean diameter has been determined. V L SCF-FA-0602 380 The resulting figure represents the diameter of uniform spherical particles which, for a similar weight of dust, samples have very closely the same equivalent surface area as the original particles. The formula used in finding the surface mean diameter is as follows :-- 51 d3 Surface mean diameter = y-jj This figure is always a larger value than the arithmetical mean and is a measure of the specific surface of the dust. The specific surface is the factor which determines the ability of the particles to remain suspended. It also has an important influence on its chemical activity and in the case of dusts of carbonaceous and various other substances lias a direct bearing on its explosive possibilities. Characteristic Dimensions Volume Mean Diameter.--Maintaining the foregoing procedure, this figure is arrived at in a similar manner to tlie surface mean diameter. The formula in this case is :-- E d* Volume mean diameter -- The volume mean diameter gives us a single value specifying spherical particles with an equivalent volume to that of the original dust particles for an equal weight of dust sample. Particle Specific Surface.--Consider a mass of identical particles having a characteristic dimension (side, diameter, etc.), Calling the total weight of all the particles AH' and density Su the total surface AA' is the number of particles - - multipled by the surface area of each KLa. iv AH' AA' = kStL the constants K and k depending on the shape of the particles. For any given material often remains approximately constant over a wide range of size ; hence need not be known to compare the specific surface of different grades of division. Let AIV be the weight of material passed by a sieve of mesh width l.v and retained on a smaller sieve having a mesh width /-. If the ratio docs not exceed 2, . " `s . little discrepancy can be introduced by using the arithmetic mean giving:-- A'AH' AA' = kSt {I-1 + f-8) 2 A'AIV "AtS^v. ' Where A.4' is the surface of the fraction of the weight AH'. One should use a series of screens so that AIV for each screen is only a small fraction of the original sample. The total surface is readily estimated by graphical integra. tion, i.e., by plotting as ordinates against W as **AV. abscissx, the area under the curve, multiplied by ~ is the total surface. 1 If the particles have the shape of a cube or sphere the shape factor-- is 6. This is frequently used for all shapes, but is 7 to 8 for powered coal. For flat particles, e.g., mica basing, /. on the average diameter of the large face--^is 55. The Industrial Chemist, October, 1939 If, however, a large fraction passes the finest sieve, the summation will not be accurate, since the specific surface varies rapidly with diameter at small diameters. ln a great many cases in dust control work it is required to make size analysis of a sample, giving, for instance, the percentage of a lesser range than the 10-20 micron range. As the British standard sieve of 300 mesh and the American screen of 325 mesh have openings of 53 microns and 44 microns respectively, it is not possible to study the problem by this means as often less than 10 per cent, of dust samples will be retained by them, and the rest of the sample, which is of the most vital range of size, will not be entrained arid so cannot Ire differentiated. This is most important, as size is the factor which perhaps influences health and well-being more than any other. The size causing lung damage is from 0-5 to 8 microns. To enable the required separation to be made, the process of clutriation is employed, using either air or water at the medium. By feeding the sample into a rising current of water or water at constant velocity, certain particles fall to form a residue, whilst smaller ones are carried over according to Stokes' law. By running the apparatus at a series of velocities, the sample may be divided into a number of fractions far beyond the range of mechanical sieving. Study of these fractions gives most important information as to the behaviour of a dust in filtration, precipitation and health. With air-borne matter in the free atmosphere, the dust sample is somewhat difficult to obtain and is, therefore, small. The measurement of this is usually done by direct optical means by microscopic projection. ln the case of smoke and fume particles where the size becomes extremely small, and at which stage the optical microscope becomes inadequate, we have to resort to the ultra-microscope which renders particles down to O'001 microns visible. Even with this instrument no definite outline of the object can be seen, the larger particles showing up brighter than the smaller ones. Perhaps the electron microscope which has been developed in this country and in Germany will open up new fields of study in this direction. With this instrument it is possible to obtain useful magnifications of the order of 30,000 diameters as compared with 2,000 diameters which is the limit for the optical microscope. Sizes of Some Industrial and Other Particles Microns Cement dust 40 Tale dust .. 10 Sprayed zinc dust IS Silica dust .. 5 Coal dust .. 5 Flour mill .. IS Alkali fume .. 1 to 5 Ammonium chloride fume Zinc oxide fume .. 0 01 to 1 005 Condensed tine dust 2 Tobacco smoke (tar mist) 0-25 Laws of Behaviour of Air-Borne Matter When studying air-borne matter it is usual to group it into three general categories, but the limits of demarcation are not definite, one category merging gradually into the next. This classifying into groups, though not strictly scientific, is very convenient by virtue of its being descrip tive of their mode of behaviour and also because it refers to their origin and to the process by which they were generated. These groups are : dusts, fumes and smokes. Dusts Dusts are particles which are heavy enough to fall in still air with a velocity due to gravity varying from constant to increasing, depending on their size and form. The general laws of Newton referring to gravity fall are usually not applicable for objects less than | in. (7,000 microns) in The Industrial Chemist, October, 1939 diameter, and are of little, if any, importance in considering dust. The influence of the viscosity and subsequent friction of the gaseous medium of suspension, which is usually air, is a factor which is of utmost importance in the determination of the rates of fall. There is comparatively little data concerning the exact rates of fall for particles below this size ( in, diameter) down to the 200-100 microns diameter range, where Stokes' law comes into operation. Study of this size range is still in progress, and in 1929, as the result of careful experiment, Prockat developed this formula -- c _v/2gciSj 3AS2___ C = 24-9y'Z)S1. Particles of this range of sizes are, however, not of much importance, as their rate of settling is very great, and with the exception of liquid particles (rain) are very rarely found in the atmosphere, though they do occasionally occur as heavy industrial dust as the result of certain processes. Below the 200 microns line is the great majority of air borne matter that is of a scientifically important nature, and this range extends down to particles of approximately 0-1 micron. Below this infinitesimal size particles are of little practical importance, not having any appreciable effect on health or industry. Stokes' Law About 1902, G. G. Stokes formulated the well-known Stokes' law. This law states that particles of such size (200 microns down to 0-1 micron) will fall at a constant velocity, the viscous resistance of the air balancing the downward pull of gravity. This velocity will be in direct proportion to the square of the diameter of the particle. For different materials, the heavier particles will fall faster, but if at equal velocity will be of lesser dimensions than the lighter particles. This law is only exact for spherical particles, but subsequent experiments have shown that particles which do not vary too greatly from a spherical shape follow the law very closely. They include fly ash, silica and other materials of a crystalline make-up akin to them. For materials whose dust is of a scaly or fibrous nature, suitable correction factors must be brought into consideration, because these shapes assume a position in falling in which they encounter the maximum air resistance. Stokes' law can thus be expressed as :-- For air at 70 F., c = 300,460 Sjd* C = 0-00592 SjD2. In applying Stokes' law it is apparent that the upper limit of particles size is dependent upon the density of the medium of suspension, as well as that of the falling body. The upper limit for fly ash has been determined as 100 microns, and for water droplets as 200 microns. It can be said that the rate of fall of particles depends upon the following factors: the size, shape and density of the particle ; the density and viscosity of the medium of suspension ; the gravitation attraction of the particles ; and the nature of the fluid flow of the medium in the vicinity of the particles. The attraction of gravity can be assumed as constant, although the separation force on the particle can be increased by centrifugal force as is applied in cyclonic separation in the ordinary cyclone. The nature of the fluid flow is brought into consideration in applying centri fugal force as a means of separation. This is either viscous r turbulent, as is indicated by the Reynolds number for the existing conditions. 381 The rate of fall of small particles settling in a fluid when the flow around the particles is of a viscous or streamline nature is proportional to the square of the size. As the size of particle is increased, the motion of the flow becomes turbulent, which causes an increase in the resistance offered by the fluid and the consequent rate of fall is less than that calculated from Stokes' law. If the motion becomes 100 per cent, turbulent, the rate of fall is propor tional to the square root of the size of particle. The rate of fall of particles under only partially turbulent conditions can be calculated by using Stokes' law as a rough approximation and then applying factors of correction to allow lor the degree of turbulence. It must be remembered that Stokes' law assumes that the fluid which is the medium of suspension must be continuous and of uniform viscosity. Fumes The line of demarcation between the matter known as dust and that known as fumes or clouds is not a definite one. In the 10-1 micron range we find fumes as well as dust. This range is, perhaps, the most important when considered from a point of view of human health. From the 8 micron size to the 0-5 micron size is the particle which, if its concentration is sufficiently high, is very dangerous to the lungs. Fumes are very unstable; the individual particles conglomerate to the order of 1 to 10 microns, and conse quently settle out steadily in still air. This rate of settling, however, is so slow that fumes may be hindered or even prevented from settling at all by convection currents. This inability to settle out renders particles in the region of 1 micron and less to come under the influence of Brownian movement; this means that it is subject to the movement of the gas molecules, and in the case of fumes in the .free atmosphere where there are constant convection currents, they practically never settle. The mean free path of gas molecules is in the region of 0-1 micron, and where there are no convection currents particles approaching this size will find less resistance to the movement through the air than is shown by Stokes' law ; they will, therefore, settle faster and their rate of fall is calculated by introducing Cunningham's factor :-- c = c' (1 + A' ) where c' = c of Stokes' law. It must be remembered, however, that convection currents are the ruling influence in the gravitational settling of fumes. The particle size of 1 micron is generally accepted as a critical limit for gravity precipitation of matter suspended in the open atmosphere and that only on aggregation to this size will smaller particles settle. Smokes This range of air-borne matter is the most difficult to study and classify. The particles are so minute, being from 0-3 micron to sizes beyond the limits of the ordinary microscope, that gravity has little effect on them. They are bombarded by gas molecules and driven about at a much greater velocity than by gravity in a continuous Brownian movement. The larger diameter particles from 0-3 to 0-1 micron do settle when suspended in an absolutely still gaseous medium, but this rate of fall is so small that it is generally assumed that smoke is subject to Brownian movement all the time. By using Stokes' law with a suit able Cunningham's factor, a particle of 0-1 micron with a density of 1 only settles at 0-00007 ft. per minute in air at 70 F. W. E. Gibbs has said that smoke particles of 0-025 micron will only settle 10 ft. in 30 days. The behaviour of smoke in air is gradually to diffuse. The 382 The Industrial Chemist, October, / 939 rate of movement in diffusion may be determined by the formula of Brownian movement, given below, but this is not of great practical value ______ / _l__ .4 = ' N. 3~nr When A = distance of motion in time t, R = gas constant = 8-316 x 107, T = absolute temperature, and N = num ber of gas molecules in 1 mol. = 6-06 x 10". Smoke and fumes, though in some ways the most destructive of air-borne impurities, do a great service to mankind. Without particles of these sizes there would be no nucleus for rain drops. In fact, without them to form these nuclei it would never rain, and the earth would be continually enveloped in a cloud of vapour. Electrical Characteristics of Air-Borne Matter When dust is blown about by a current of air, it becomes electrically charged. The magnitude and sign of the charge is dependent on the nature of the dust and the electrical state of the atmosphere. While this charging is taking place, the air or extremely fine permanently suspended particles in the air become charged with the opposite sign. A great deal of data on this phase of dust research has been obtained and classified by Rudge. By raising a cloud of dust by means of a blast of air in a brass tube, so that it impinged on a fine Wire gauze basket, he was able to collect the static electrical charge on the basket. Then he determined whether the dust was charged, and if so whether positive or negative. In all, he studied the behaviour of almost 200 different specimens of dust, and summarised his experiments with the following conclusions :-- (1) Nearly all kinds of finely-divided material when blown into a cloud of dust by a current of air, gives rise to electrical charges upon the dust and upon the air. (2) The nature of the resident charge upon the dust depends on the chemical characteristics of the material. (3) In general the charge obtained upon the dust is opposite to that associated with the " ion " of the same when in solution, strongly basic bodies (e.g., limestones) give negative charged dusts and strongly acid bodies (e.g., silica) give positively charged dusts. (4) In the case of salts the charge apparently depends on the relative strengths of the acidic and basic ions. (5) Similarly constituted bodies give similar charges. Charges Generated on Moving Dust Particles Carbon .. Copper chloride Potassium nitrate Sand .. .. Sodium chloride Fine soil .. Sulphur .. . .. .. . .. .. . + + + + + + + Aluminium , . Aluminium oxide Dextrine .. Dextrose .. Iron .. .. Iron oxide .. Magnesium .. Magnesium oxide Sodium carbonate Zinc .. .. Zinc carbonate Zinc oxide .. .. .. . .. .. .. . .. .. .. .. . - -- -- -- -- -- - Dust may. become charged as the result of friction against a solid surface. By this means electricity is developed in grinding mills and pulverisers by the friction between the material being ground and the components of the machine itself. The fine dust which always escapes is electrically charged, and if the machine is not earthed it . also becomes charged and in very dry atmosphere of low humidity, discharge is liable to occur. This may have serious consequences where the nature and concentration ofjthe dust content in the air has explosive qualities. In practice it has been found that charges of ov 10,000 volts can be accumulated. Such charges are oft^ found upon the filter bags that are used to separate sum1 dust from air. These bags act as a kind of electrical machine separating positively-charged dust from th negatively-charged air. Similar charges are observed in threshing machinery. Unless steps are taken to humidifv the air in the zones of working or by the designing 0f suitably earthed collecting apparatus, there is every likelihood of the dust being ignited by a spark discharge.Y Cohen has shown that the nature of the resulting elec trical charge of this type of friction is dependent on the relative dielectric constant of the dust being generated and the material used for the grinding components of the machine. The material which has the higher dielectric constant becomes positively charged. These rules apply to liquid particles in the air besides solid matter. When a liquid is disintegrated or atomised the increase of specific surface (since the electrical capacity of any substance is proportional to its surface area) is generally associated with the electrification of the droplets. The ordinary thunderstorm can be explained by this principle. When large raindrops exceeding 4,000 microns are flattened and disintegrated by the resistance of the air they become positively charged. Meanwhile the air around them has become negatively charged. During the violent vertical circulation that occurs in a thundercloud, the positively charged droplets travelling downwards become separated from the negatively charged air that is carried upwards, so that the potential difference which accumulates between the upper and lower zones becomes enormous and the tension becomes great enough for a discharge to occur. This discharge is what we all know as lightning. Similarly, when drilling for oil, the surrounding atmosphere becomes laden with minute oil globules, and when a discharge occurs we have the pheno mena which has become known as " The Holy Fire of Baku." (To be continued) STANDARD FOR PETROLEUM JELLY IN the series of A.R.P. Specifications which the British Standards Institution is preparing at the request of the Home Office, a specification has been included for petroleum jelly. This compound is intended for sealing doors, windows and other cracks in order to make them gas tight. The specification lays down limits for the various properties of the jelly so as to ensure that it will be capable of being applied easily. A further specification in the same series which affects the oil interests is BS/ARP.22 mixture for anti-gas cloth. This mixture is applied to textiles for the purpose of rendering them impermeable to gas and is made up of lanoline, together with a heavy oil. The detailed properties of the oil suitable for this purpose are set out in full in this specification. COAL ANALYSIS FUEL Research Survey Paper No. 48, covering the Nottinghamshire and Derbyshire coalfields, has recently been published by H.M. Stationery Office, price 3s. This report forms part of the general survey of the national coal resources and records the results of the analysis of 277 grades of coal from 17 collieries. The survey proceeds roughly on two lines: analysis of coal awaiting exploitation and a survey of the coal delivered by the various collieries. The present report deals with work of the latter type. The Nottinghamshire and Derbyshire area produces coal suitable for metallurgical coke, high-grade gas and house coals, locomotive and bunker fuels and frefj burning coals for steam raising and general industrial purposes. 416 The Industrial Chemist, November, 1939 Air-Borne Matter, Part II Characteristics and Industrial Implications By Henry L. Muntgomery Larcombe INDUSTRIAL process air-borne matter covers the whole size range from heavy particles of J-in. diameter to indus trial smoke of sub-micron dimensions. Because of the extreme diversity of kinds, sizes, shapes and densities of dust, variable percentages of concentration and different volumes and temperatures of the gaseous medium, almost every problem in this branch requires individual study. It may be that the dust is the direct commercial product of a process and should be retained for economic reasons, or it may be that its dispersion in the free atmosphere would prove to be a community nuisance, and with these and other points in mind it is for the engineer to design the equipment on a practical and economic basis. These collecting or separation methods can be classified in the following manner :-- Method Equipment | 1 'article Size Collected Inertial .. Filtration. Sprays . F.lectrical. i Cyclonic or centrifugal | Down to 60 microns, dry apparatus ! method Down to 5 microns, wet method Filter bags Down to 0-3 microns Scrubbing towers Down to 0 2 microns 1'recipitation , Down to the smallest detectable dimensions Gravitation The gravitational method is exemplified by the ordinary settling chamber and is only applicable to mechanical and solid dispersoids because its effectiveness depends on the rate, of fall of the particles and, as has been pointed out, this rate is dependent upon the size and weight of the particles. The rate of fall becomes so slow for the con densed dispersoid that it makes this method impracticable. The actual rates of fall are from 50 to 60 per cent, of the theoretical as calculated by Stokes' law. It is evident, therefore, that particles of 75 microns will have an actual rate of fall of 0-8 ft. a second, and this is too slow to use this method. Settling chambers should be designed to give sufficient settling time for the smallest particle it is desired to remove and this demands that chambers should be made wide, and low rather than high and narrow. Wire curtains are often fitted to minimise eddies and these also tend to remove the finer dust through contact. The actual settling rate of the finest particle to be collected should preferably be determined experimentally. W'hen this is not practicable, but where this particle size is known the theoretical rate can be calculated from the following approximate numerical expression for Stokes' law :-- D2 S C=#X60 Thus, if the smallest particle to be settled out is 50 microns with a sp. gr. 4, the theoretical rate is 1 ft. per second. Assuming 50 per cent, of this figure for the actual rate, the result is a figure of 0-5 ft. per second. Inertial Method Although with certain apparatus some condensed dis persoids may be collected by the inertial method, it, like the gravity method, is chiefly applicable to mechanical dis persoids, but on account of the much larger separational forces available, smaller particles may be collected. As gravity is the separating force in the settling chamber, so centrifugal force causes the separation of dispersoids from the gas in the centrifugal apparatus. This force, being directly proportional to the gas velocity and inversely pro portional to the radius of curvature of the gas path, can, therefore, be made very large by designing the equipment to have a large , gas velocity and a small radius gas path. Although Stokes' law is not strictly applicable to moving gases, it can be assumed that in this case also the resistance to the motion is proportional to the effect of the net force and the resisting or frictional force on the same, factors. On this assumption the separating velocity in cyclonic or inertial apparatus corresponds to the settling rate of the gravitational method and may be expressed as-- S D2ZY2 Separating velocity = 1 -- Since ZY equals the tangential gas velocity V, the above relations can also be expressed:-- S,D2 V2 ~ QZH In the inertial or cyclonic apparatus the important factor is not so much the separating velocity but the " separating distance " that, the particle will move under the action of the centrifugal force in the time the gas remains in the apparatus. There is little data on the distribution of gas velocities in such gas streams, but for the purpose of approxi mate calculation it can be assumed that the tangential velocity is constant, that the avtrage time the gas remains in the apparatus is that required for the gas moving with the maximum radius for the maximum angular distance U. Furthermore, while in the inertial apparatus the gas path may be simple and almost parallel, its path in the ordinary cyclone is very complicated and involves a double vortex. It is highly probable, however, that the majority of the separating action takes place in the outer vortex, so we may consider the gas path in all apparatus as simple and approximately circular. , Considering the above remarks in conjunction with Stokes' law for moving gases:-- cSepara,ting dvis.tance = S,D2U--V For a specified gas and a uniform size of dispersoid this simplifies to Separating distance =- QUV Process Dust . The table on the next page gives cyclonic values for al^ of standard viscosity, spherical particles of sp. gr. 3. R J18 been assumed that for the above conditions Stokes' la" gives values of twice the actual values. Filtration .. The filtration method of dust separation is genera ^ considered a sieving action and this method is well cxenip fiecl by the bag filter system used in processes of every kijV The bag, or its equivalent, is a screen or sieve of cer , size through which the particles like gas molecules .; The In certain but whi method ; part. I greatly filter. The a baffles is design o. formula; only gui method. Dia. ol particle SO 20 10 1 100 50 20 10 100 50 20 10 1 100 50 20 10 1 100 50 20 10 1 A filter These pas oil and tl: saspensioi retained 1 Wulating m :;.i dU-.'..'. iiytionnr/'V iber'. sb .iis-frhiiri-;;;: :cly i>rb-; ' ' .The Ind'jslriai-Chemist, November,. 1939,)'. S. : , . / .7- cV't'Wih//iciisp'crso'itlS ySma116fc`ulii tsf. :/bri'K^y^-'"ciV- ^^9^' i C*l9"S r'//:j i i-bothixl- coljeU'iphyhy. f:/s<:t: a rV;cl lic^ion ohi-.-s ^ P.: Ja rgb ; iiWT"t' ft ion Her>irii'e:diTii n-irti'f-yfTl t rVi-tip'Or;^i t'seiJP-i5e'c^ ri^s .fr|-!;:i'.lyl dcperOfeyHijVon/! !:''.. porUoii:; r:yt.:.u*'r\;h >51: ! hti fZ'j'P&s; "c-fc ;Oy'-'j'lici''abiliiy.:6'fy_d us t'.]i;i.rt ii.'tasbtiri ifej''cvfci'',clbt`h'ra.ni1':.() blicr vjMfflfe'!> if'ficJ.i i p.W] form irhi.;'tc And ii tyscc'nis';l:1vsT:;m th e "K<jSii^n:^.(rG^iifipm^nV-.o'lf;f his^tint-t'yfeV-i2X]p_crj6riceXjLiit;l:c'rtipiriciii for:mil.i-.. .(leiyrrniiiicbl^yy Jxsiio';; /: i;ci' rii;;bruv.l:...reisi;:in (.ric. ''iohil^V;g!'1'i<i'e^',rto'-Kth'e.Ji>i;pibfei;i'|Sp>o\f,^'cl\istJ7cli'rtimu'tiryn-Vl>yVij-JVis" lnertml Separation 'f'&sV v-"- /t; an eni:`f aiy:;j},rit' ;'.ya)oity;:7ip :r: fcjepn'ratin'K. /-`J .r^.'r ' '.`SJ' particle .^;`.:X.3istrihce'j.".'> v' fj =W;rc*.i'ViVlip'ris y- /jl-J ,=:.(n'rail ;X>aU'i.-y iiyjvin;: ;:isista'nCf'.v TiCt-dor'ce : 'cyCfenicy. :/;:rateyc>i ; frfffyf.' f'Y/Vf.fnifyyy fffyyiW i20 <:r/frr:6\.$r bi'O'i'i" 111 oft y'--7i ov.;? ArA^r/.o'.-Sb''-' \y};\7f)tyb yy;7l;30077 r7:';i66yy .-vf. i'Mi'w; 7:'.A:"7AI in "i:.r7bv7i;t!.y;V:.v/ '.t-y-X;.:A2bo7 yy -b^`ior.;r.:.nb;d '-/so 0.' -7 yy.yscoOfiyyyyy;; ;::;y;--8;oi)dyy ' be'.ibbvu" -;<sa' ..Avro-'b V,::.v; Kfr&V-'" n:7':A>l^0AA':.;y::: OVt-XlC v.^y/AStfyf f r,- f>s;oo0 0 y2.t y - s. ':;Vo!G,'ppff;:v faC'ipf;-;-: ipCoty.'; ii/ill'CVP: ,pri|xi->; /eiiiiajyf; niiiinsp-' gf ivitii r'joH:y'l Vyfr'tiSi oly-'n' H'-'rSt).-:.:; '(f ft-W 'yiff-yyixi s/AWr:' -y :.: I;;]; :Jf'pa,Offfl.-?.:=V V =;Vi: K;;'i6 ZfyZ'f-io'ic'.Vy.-y iv'".:o':7yS'y; Vv.vSft'.;.-':. :ovv,'-'>6yo;; VWyyvry- -'ir rO X'Vff'j-, ;:.oy>y>jy,oy:y;s:;; '; '204 ;000 -: iicaVjLO-; yjipA^fi lie r-Xwi I'h y.V.iijizag'; fjii'ssages\yliSs';'a^ .'s'.patlV;:; ;. i TJiesfcjs;j>iis5yigesrifrft>6pv^erea jjvjClVyJ-iV^prj^ ::i>yig:ti ci.SV+i.oii^dfyin^ '';;d!.'andbHep:hAi';:b :>fr.cirbci:iuri: ij. the- .itierlixi:i.i' cf (lVjVii itcyi wj'M'ity; yoriex'r / - i ?psp:on^'ro'n;;.i'_eSi.rl ts iih :tiie,-ii ust Vp.'uii.cfcS'imp'iflpn^.-S'ri'rl'.bfiirVg' --.t ^ ' \UC^lV#f,-i'I'!-'.'0'Sv?L" rJja'1ir.f?!:!vf:h=e'f pf'obltfrnai'of jifo'i'?-.'- ;n:Uiar.iis-.h; i hem.iti-iVitiy ` tIn': iliobry.'.oi inin'i osiu'plp;. mo '.'.Will! Particles ofisiUca rock-x-79- ;'.%6KlikcV;tftu'Upt;p_s0in^''ani,y:eXperieH^'^Lfp'it1i;byh'HainA,iFa'c'(o'rs:'(Sf ysi.iCi^ssM'::cipsignV;A;yprJ>y:>.A.:6,y:^ Spray or Scrubbing Method - y5'-y<-:-l rijtli is_>rri.t?ilVo<3 ;.t)i;crjSriirttipj[e_'o'f5ri'perfii. nV'is.oKiin17.tl'i'e .-1yi'St' opayiiclcs: farjiy.:ca ji 1ftvby/;wa ter'- clrpjilqts^rpmyrSprii.ys'owhidi' he'.d. .ihe iV,yrt.icli:':by..hie:iiis of il <. i ;-.':b ie:isibnnti >, \!vi viii.u ;i: D.r":nI f'l poiss;i (iTitiy'ihe : r{ c 1C';it>>' it.;set!;c. '.do-' .'r jprisi'tiTi^y'thft/Xlfiiit;Vipft'o'-'.sjbo'cia_] lio'pper^VorTsirnilar/iiycVicivrt-^!' '/ri:ti iiiai:: iir-f lic .seiiyrt.iiin'Of. fhiR' iypc bi oiyuipVnir.y . i.-^ ib.O: PiTUiir/: </i 'rho. cb-.-ii:';to. bp 'odlleciixby Aay niatrrud .-;/wl\ic ti;/sXpo pici aYjrih'gecl"^''Di^ixeircibr'ecl';'ii i'vjj'tj cc5fmriif/ri-1.fiJy' /.&tiii ;!bR'yV tfol 1 ortyecl -iliS S :-0'!-.=^r HiSyaiiriert! wij'V'of; :]eli tty I fit ?orV J.'and j'ci'oUeC t iii{^'.:`isy; yisua.I ] y'--'us<%cl V/f6r'Ar.fli.1i; ;ga'ses! Tr.e ciiecnypness pt .t.l!1: s'iM^iv uicihiJd 'ioes .Ao|.ldep<;'r.'<i =: nt :Vc1 y.i;p-:.iy.ti:c: c.6:r t/ir.t -b:iwf;c'n cl=iht nncl- \v:11 er ilroplefsi' 7X'iigreff^ : fiiw::<;'611cct'iiig >is; ci iie yto i i;iV(yrnge^^n.fc'.. VAhy,//ipnl'act''qn'^ 'palsspgei ;a.;iid j^o/alterlnjc_'!d ii'ectipji oi`flowio f itho /{jajsertiVs! :-piVidjj iimiy,.' :Ii c-yjjartj6i fts^imp'inlje^c !'iifs'-'th e. 'p':iss.!h'CS; by f hi?ir .cvyri . :ii-;:-ji:i. .''l-'iissrig:'gasos -.throa.;!, ynunigh; fiiios/or-towers !':li:Ci.!\vitirs|ir/iy>.iivv'cry\ii\oiti:>i':.vii, .bee;,nso- j ho, fliyvpcrsoK'.s'i re ns!i:-.l!y. s'Vrroiiridci I I<y . ii c:i.s C fil tilVvvh iiili '.i:6:/j5re\^cnit'x'tii'Mir '.en'tj'a.irfn iii'n'f ' /.The :ir.*rr=..y ci..i:a!ict is pariicoiarly well suitea tn-'aci as; .oaoSitcOud sU\'K'}-'(:fiSier.tc'r itv;.cx'oVP.i:'na!icuvv;iUiby''oyptbiHV'or ' sivnile-.i' .dryoriofl'idd'-oisiiiVJfti.a-i::Sejia.'r^tt!orf .Electrostatic .Precipitation 'rhis'mV:*Lod/.rilthpi'-.'yh.ir:\-est:arc11;:1s lomr ago its 18I9.; i.sf il'.i:' i-bOHl :V r*l aii V:rr.ctic:ai.sy:''1'!!*ris .<' coiloccinlj 'aft'rijornb (illcriyvTh pp\yfei' I f ?ln>;.yslbct fifedy-g'ticjcy>"bif!. :i:sep:i i rig 'Svpyi; {-r<'Ict-yd ,ust '.:svei l /Joio\a/ii'^'^Eincl >G;-vS;:.vJ^o fi ni-; ftsciuq/l lii!;iir:r:li!.<p:iPir.:l ;a'ric; Gaugajn cxpvfr:tiientcc:l 'with.';;|j_iis';afij:i 6f i levkp paratii;syvpfoyyrijtf '.tK.n.t.^fJt-Jn'ci UrtjLio'ft''-Was';' U'P si'.ion!ific p isSihibry. :I'ii.`jjioiii.-ors won; .heid. up. b)v:.inf. :;ufc(jiia I;d i igh/r-tfinsl Cinyy-jSp'pjyrjl tuB'.'-fmd.y'.insirititfirs/^ asVd J;11Vc''. <IcyJiij>rf:cn{ of ck;:.'u';C:il !eel:ri:c|ue w;iV t.};..:.:fartr>r \v!iich.. V/;'. , 15 ; .-cl! csceir^1 ye-ofocr!^ f.ar/ichs'6fjgypsiim':y(}'79. - bhaliofl the aijpii'c/tno'n 61 'ihiSr'pri'Voipjr uiln; 'f.;:c;:T:-a':a'n;lios ' ,ot 'Oj' ii'ftll.. I/jV.^^/o.vo.I ;:o o(.';:;';v''isia'.;c 'pn'.d|'..ita;- ' ..fio"A';ccurhpig'.a'p:.CMfiiiH,.rc.ki' .j.'i'ojX.siboii.- - . : iibniy! 'doi'.i.ric:'.! poi'T.ii'oil /rlil'f*.tjicc >is; in:iiiu-i'incc: '-anc - .'.ai'r.;ii!; spf .iii>. H'Ci.\vo:,;ii fv.p; tylccuopU^syinsi.iintoclifbyn1 o.acl: ! .'0!.]'.(:i;'; .\iiVi iipryvccn vviplcii'. the' gris is 'r.llowod .;' y>a:ss.j-..11; :;:yp'i;dj(i;iry.vci^ r-v^'the7fi fsi*JVa fgey\fcle;ct.rord<i of jariia11 -.^osy^Sif'ic'ticin:;a'rti'ri'7ati:d j 420 curvature like a point or edge, so making possible the high electrical field at its surface which is necessary for the ionisation of the gas. The other, which is called the collecting electrode, has a lesser or no curvature and serves for the precipitation of most of the separated dispersoids. Mechanism of Precipitation Due to the high electrical field, the ions formed through ionisation by collision near the discharge electrode, and of the same electrical sign as this, are carried over through the gaseous medium to the collecting electrode with a velocity which is probably more than 100 ft. per second. When the gas between the electrodes carries dispersoids, the ions attach themselves to the particles which thus them selves become ions and are, therefore, also forced towards the collecting electrode. The velocity of these ionised dispersoids is naturally much smaller than that of the gas ions. It is, however, considerably higher than is ordinarily surmised. Since the gas ions are molecular, they are smaller than the smallest fume or mist particles. The number of these gas ions ordinarily present in the gas of the precipitator is also probably many thousand times larger than the greatest possible number of dispersoid particles in that gas. By studying these remarks, it can be seen that the effec tiveness of this process is not limited by the size, weight, or number of the particles. With the progress which has been made in materials of construction, it is possible to build electrodes to withstand botli high temperatures and chemically active gas and so make the process practically universally applicable to the separation and collection of air-borne matter. In addition to serving to move the ionised particles to the collecting electrode, the electrical field and current also exert a pressure on the collected material which serves to prevent its being re-dispersed in the gas. The efficiency of a precipitator is a function of the time that the gas remains in the active field and can be made to approach 100 per cent, very closely. Since, however, the size of equipment increases with the efficiency, an economic limit is necessarily set which usually lies between 90 and 99-9 per cent. The precipitation rate depends to a large extent on the size of the particles and their characteristics, c.g., their surface conductivity, since sufficient surface conductivity is necessary to permit the discharge of the dispersoid ion when reaching the collecting electrode. This surface conductivity is perhaps the most important factor; where this is inadequate the addition of water or other' conducting material which can be absorbed on the dispersoid surface increases the surface conductivity and greatly increases the rate of precipitation. The particles having arrived at the collecting electrodes adhere to them and are dislodged in most designs by rapping. Certain classes of dust are removed from their gaseous medium of suspension in such a hot dry atmosphere that either their own weight is sufficient to remove them or comparatively very light rapping ; in most precipitators, mechanically-operated rapping gear is required for both dis charge and collecting electrodes. Liquid particles which are precipitated require no removal apparatus, but trickle down the walls of the tubular collecting electrode. On being removed by the rapping operation the particles must not be re-dispersed. In ultra-high-efficiency equipment, the precipitator is divided into sections which are shut down during the periods of rapping and are scavenged by an air blast thoroughly to remove dispersoids which may still adhere before putting the section back into service. With careful design, however, this is not necessary in the majority of instances. When the gas flow along the tubes is streamline, the gas velocity is highest in the centre The Industrial Chemist, November, 1939 and falls off at the walls. With this low velocity at the wall, it is possible for particles to gravitate without hein,, entrained in the gas stream. Another reason is that during the period between rapping, particles adhering to the collecting electrodes agglomerate into larger particles which gravitate more rapidly on account of increased weight. Numerous factors effect the design of equipment of this sort, the principal ones being the volume, temperature and analysis of gas, and the composition, size and concentration of the dispersoids. Almost every process presents a different problem, great variations being obtained by relatively small differences ia conditions. Sound Wave Precipitation In addition to the methods of collecting air-borne matter described, the United States Bureau of Mines is developing another method of precipitating fly ash, smelter fumes, etc. In 1866, Kundt discovered that sound waves passed through a tube containing fine powder will cause that powder to concentrate at points free from vibratory motion. It has also been shown that high frequency sound waves affected the diffusion of solid or liquid particles in a gas. With these facts as foundation to build on, the Bureau developed its process, initially for the purpose of treating smelter fumes. It consists of simply passing the smoke or fumes through a tube in which stationary sound waves are maintained. The tube must be carefully proportioned, however, and must be of such a length that the waves reflected from the upper end are in phase with the original sound waves produced at the lower end. Furthermore, to get the best results, the wave-length must be approxi mately equal to the diameter of the tubs. For a tube of practical diameter the frequency ranges from 3,000 to 20,000 cycles per second. To set up sound waves of the proper frequency a shrill air whistle is used. The sound waves produced by this are reflected at the top of a closed glass tnbe, so as to be in phase with the original wave, setting up standing waves separated by planes of no motion, called nodes, spaced approximately half a wave-length apart. In its complicated movement between nodes, the suspended matter collides and thus coagulates, the heavier flocculated masses finally collecting, at the points of no motion. Dust Explosions This hazard is found most frequently in coal mines where fine c.oal dust is mixed with inflammable gases. It is not, however, limited to coal dust or to mines. There are dusts that are to a lesser or greater degree explosive, and in fact all carbonaceous materials and other substances which will bum must be included among the dangerous dusts. To this category belong sugar, rice, cork starch, cocoa, wood- dust, malt grain, wheat-flour, tea, spice and numerous other common industrial powdered materials. The fineness of the dust or degree of dispersion is of con siderable importance in studying the explosive hazards of air-borne matter. The finer the particles of a dust con centration are, the larger is the area of the dust particles and the more readily' a chemical reaction with the oxygen of the air takes place. The most characteristic property of any explosion, how ever it may be caused, is the ultra-rapid, almost instan taneous generation of a sudden increase in pressure. J"1S may be due to the production of an increased volume of gaS which may shatter the' confining walls of the containing structure, or it may be due to the impact of a wave 0 compression that travels through the gas with a velocity equal to or greater than the velocity of sound. .n There is little increase in pressure if the combnsti occurs so slowly that the heat of reaction is dissipated rapidly as it is produced. It is obvious, therefore, The ln< the rnori will be t: ;. these rei duced by of a giv' favoural: tion of a The e: to the ra the expa originally when com of suspen through t particles, centration finely div: This occur of igniting The pre dust is ma volumes 0 tempera tu it produce of starch violence. ' With ce: 'Ms'-Hhat;:-:: 'jK.tf' the . ts \v';v'h''. > ?%%] r0 -I; of -: t;:s. ytuY6-rind;':;' ;;:nfcitKwY ; !:n. ytfferp'nces;. ;. The Industrial,Chemist.povehiber,'1939 id. ;,y:. yd-'.'/ : ' . y fi^'.^ciStiy&us .hio ri'cjta fees'jplidce j'_h igtieir.; ^.jil-bc-.thi' nuixin'.iiin pi c.-5s;;:;e of : the react jun. Considering Tyiinarki, wi/ may regard the inyxirininr'pi'eSR'ure pro iict;cV;T?37i''P19S`iori ' a.i:' a'r'lTirVtts iir<ipof; < 11o' ;iia fla filp-i'^ bi 1i ty ,^{ ,=adpi.YycYi;y<liistp'itin'dcn fj pr;rilYidntii i kfeyiid itifJiiS O'n ly"ir.i Yr,sMYunib!'a.cin:u!r':xl.anCi > will cxpk'sir.ri rcsuil. in-the lorhia-. 7(diV7pfdiYd(it6nrti:i6hrwdyc/Y<YV;V;;r`i;/;Y7Yr^pY:7;;yy;>'Y7YY;p;;;. -'.Tfi :.".{xpa'nSib'nf::! pFcssVi Id;Y ;i!sV;pi1o'cl i icpsrl >[is i,.tl 11 -rei i: i i p.r; tl>e drapM ifpniia fioYi In: iVxpruision. of iV.c:air/oy ti.e. heat c.ii ycaci.trin.:: 11. was 421 he nt/utcri i iifhes; :ctc;;'..'V. ;s ;'passcd V;7; /diiie.'diiU'/ri; '' y tiro tirfnj' -.'ml wayeV. '/ 'Particles.of, carborundum is; .79 pin' avgas': pc'-Buredu;;.:' 1 1 iins' : :>si)Yoke rir.p; p,.wk.ves';are.;' p 'pcrtioeeui v .. .li'i: wavYs ;': dfedrigindp/ h.iiririareydV.'y yVafipririck'd : ri .(.ul :ofp.a '. Particles of e'nery. x 79-'. .. /:povio?U`7' d'origini11y.,siippose'ditiiaV ciusUcolic-erfVratuSns^.Srtlj^icixpJO'de;-; I ihch icombiistibid fjasepyverC/preseht:'in:;i.ht;.f5js.-fiPtiS'm'iiciitiin i iniaterial is !r ;nitiir..'llf:' roritacl wiih (ho ^.iS'..oui.'inedi'.;ii! .' . iii which i.` is sasper.cied -li .'*:i.rr7s l.'-n11>:-.ixihoit;:fniTi' thril iiiist disj'ersniilspvi'.l li:;ri'. wi: li niiixip-.iia yi;ldr.iiy .. wh.f.h ihi.coiiih'ii'j rilidirof tiie iictiia'. r.n'r.biis'ibie is ciiern:'-.- :ally >qnivalaai to' llie ixiccenliatiou of bxypeh in it he pas.', ioi, wheii lliis is' the e.istv.iho iviihliei . Of ri.olecr.les ii! coni-. 'hu'sthde.nuae:ial ihat iiii.iin direct roiil ic:iwil:'. irolcculesix>fipxygen hs fati ai;rrffiXimii inii {}//:;'.f. i/iipOb'ci.: ihisyisfciujyclytp'.ibeiquitle'.iyiieiiyvl'rerayp.ut y.^ ctM,t.yv^he';Cxpld'sioh,:^eisurp:'iS:'at'<i:aifrt'ximiijiri;.'atvtliiSVc6fi^'.''; ccnuhition ami liiiv.iiiishiis raiudly ias the conCenlration departs .ft'Oih rLhis - v'ubic.'in -eit llor <Jii oct iori'i . .7 i /:; ./' > r' h "c.y'r.'-shriil'- | uf ' s.;.ispciisi' !!' ; -t ti;.*.; 11 ioy ;propagated" i'ur .i'.xpjpyiori iby tiv.s'rircY; ^ihrciifili -!hta volatile .htm: It itesi:Iting. fro::i.ifo la'.111;ifi_y h; r'o i!i .IpHrliclcs. . It link now.been proved fhal: ;ii: the ooiTcr:t.'r.or;-'; MANUFACTURERS' - PUBLICATIONS ..'lifi'P'VwaycsTr '.xsi. spaced..' . ftriiplicate'd ; :-;;iPi-\ct)UidcX; As^iMyV iftmfra'UpiifirispmUahwnikira .|i'id1 yyliyit!oell bust s-aitd.the. /air.. iifhis iyciiiiis^OYi^Jifllyiihfctifivc'press'urecthpfrfcfrprn'dsiftipyhif;'- igiii!inf:.ti e. fern;: ibing ririburnt dust' particles ..:; /. ..i 1 The pressured hd/is; produced Viy aiv cxpiiosion os starch; iWipkWPim^^tficfGi] 1 tin karri p cat iildgmi N o.: 109 : vi .. {1939 eelitrv>:) i.11-,ill^ wi111 soirii-S`ii: cliernichl plant, the fiferti'si Being ,'gfpti p.fcti'iiogefiycriVLSjiifVrr.yaiio.jaossibto^uiTLcierri-iio various unit (Vperaiiotis nt <:in':niir.al. .enginec'.'in.t;;; li is.a if fei'isifnaiiily'.iiite''to-.thei. ;i'itpid ifrirm'atirripqf /relfitivcil.y^ar ge' p Co 1 td .J-o!nVneri Of. gr.lsiuiv- Sviljjl:ni'. ,on ::U:c<>mit of ii.s h'w.ignif.pr. ,r;i;:;7`insihi~d.hG:Stiirtiiyant;pu.l.)lic;it|pii'-No,';d036.:isiail2-page''V:. 'diHcsHvlicrd; yYaVpiiMtnrii/cxpfoijcs iV.pic iVadiiy/ llian StiiYchy since '.lin.ichpre giying ]V;ir`.ici'.i.'irs, diagram? and ipiiotnerapiis r.f i' prodifccs or.iy'Hali tfpY: Vc-luroc isf .yasthritam on'iial weight propeller ifans , arid isi'nali a'icctriri; veiuil-.dihg : sCfs.-i-:'. . ;';e:are"drjSji.y fcf starch pibduccs. it explodes with corresponding^./^ : .'i:lri;!n'!i'<:t' St'drliv.riKt jyninpies''.Cj.- Ltd. .'eh ' ii-.; C-i-.P, ;;i^Z.i^W^fe!i^eiNe^jSyst0Vnpof;';Harfri&i!iyi:,LigHting'."'Pis,;;i.' >;;h^iich,;^i'l!!h' j With certain' drists/hypaluminhi^ il'ot. prodii t!se : iitic o( Yt depciit idHehiainin :..lilcctrfe..pubiic:ition, ;No: i. :>7'dsv-'Ipii :^f J f)iei; c'oifiti*afy/=ii'sc -upipxygdn pfrpm'-itliei a i r;iaiKci; .)6.'i9/73;); wiiieii ;l;:is. been c.irciilatod Id ti;.c irinie- Ii. ^plosion p.-ri-sstiiel'.is due entire!}'. in the- tlicrirriiI expajisiorii provides . riiiir,ern'us. details and picturesi 6f.' the;' Ahoiier. - herons i>.d)cI/. .fl.the-air. - THe/heat of reaction of .aluniiniuvr.. dust, is of sys,tem;.rtrriri'cfil'dictrijligiii'1'n;gr.'Kiii<ijifsiap.plic_artbnSrfyi^ej"amt'>!/ri hrich'.'aMiigii order,thru, the explosion pressure is in if:e sapiio ilEicdp'rIAmpdC:/:'j`i:Ar':;.]pyf'r');'pA': diy'P^PiP/1..:/'.'ii yais'iit l>a t : St arch iy y;y..-':;/i r-;i fi.': i;;/v.' :iyiiYY'iiy'ypy;;ixi CYi-i: i i =:.i .yr'RcsCpch'J folder has Ijeerrissued (Kip-3) ii hazard? i.'ly.frijtlie/tTiajbri iy';pf ;cas'es'tifft^ :r/^ving^efrtUS;pf7/t]L/t^^y^fal8^u6'5i'<^a:Uhi:Hfc;ritcs<^i'bj'ngf-'.tKc''r>>' iaicliisli^i ffi xliiii ytcidhcfexpaiisibiipressureii'tjittfj-isiipjfoduotYd iya n <3 : ri Kipp Und Zop.en res'erirch insfriurieiiis. riejeth^ with'.brief i :s, [Kirlii;!'? 'itasunimeni of expiansiun pr.i.'tfsi ires''pi odreed by ditfofent; 7 .clesnripftioiiS ^of.'th'dyaiYpVitratiirSV hy'oif^tliri fcat:\log'u<ife' tli'pr'em'<:::-'.; ' -sSterials .un'ler.'si ahd.ird conditions provides';! satishi'etpry' listed is available uri veriurist frriin H-'.iEduards,& Company. ... . ynpine.iil 'bi'.sis foii CCjYipjali,tng;fdi,bifcxjpl0si0iV;liaisai-dYoiicacii-- CrcSta:iol-Moclifirid iphenrili ': 'si;s*-; * t-.piso is h iriethod for., the eYnripririsfei of ilio iiillain- . ; foihiiiiiLlclftIiiyclcp yrpsiti si.ti.-i.Gi'dst.ii'ricil ylVl a If:ic j-.it n'liycdrirl6yi ;-re'sins' ;i - .hhitty./bi/^ sr.irrie ..dust;;'. hdin'd-vlCrcstmiPureiitpte -`ft'* /'-bpiefri-ri'fpunci hutytiiej:pr^s'suYeVrl^vaqped' h'eri-: y..^h,&nli(?ijii:iqiii.o'f a liooklet issued rcccnl'ly by' thc.'nianu- pfaCturei'Si.i.;.,; P'a rtacrilririjai'te'hfipn p-dS;VrclraAyhiV/ttoi i:Crefetrmol if -ejf!>| IoW ing ifa'C fCirs^;.\i\l;hie'enfeterttra-ti ofiY;bfV.th e*';: iiS;Br. 226,'ydescribedhrisiiaY/yPry.'lVardf/palpii'Jri^hyvyipcpsiiyeV/ CiI.c<>1nRosit:on'o.f ii.i; cl11st;;i lue plijosical ciiriipiiSiiioii. ; imocii fled .ipHeiifoiic;^resuiiwliich': cartf lidi''cliasrhiv&iiViri i:th'e 1cc>iti : I the'elrlst V-rtiit: ctiirij>ositirin of flic at.inosphcre ; '.in'.!.'Ihe. . in solvents or'cooked direct: info starid oil at"ri low temp:ora; d; ';|!r:!perniUre. e.\ ten Sand dural ibii 'of ithb igiVirion.i ... . '; tnre. Itdcolorirretentibn is stated to.beaHot'eth'cr unusual; ^ pin iicles; nf :';i dnSI. cdoiicl,' rilthouji'r. nuiriy jl.iio.usand fir a. inodifH!i.l piheriolic'rcsir.,' ('.rcstanol S:B.. 248,cari..it:i3' ' . ^:|rtici 'iii size; tti.;Vn; tlie iiiolccules of riigris, die stili : stated! .be.used td produce very quickdryiiig iacqricrs-'ot i-, ' cr.;fd- U; fWedin^iy sipall.'iviii, `ti.c Vesih- il-.ai ^ tiie finely diyided /great' durabilityy--.Ntriii'/y.jarr 6-;'C'i.':!-td!r:r . :// h' ihi /.'.: THESE MATERIALS UQVIDED BY BALL STATE UNIVERSITY LIBRARIES . NOTICE This maH ena` may be protected by Copyright Lv.\ 11 t`lj 17, US Code) - . - . The Industrial Chemist,-December,:/939 Air-Borne Matter, Part III Characteristics and Industrial Implications By Harry L Muntgomery Larcombe - IT- has boen-'pr'o\\':d ^ .. _ y\-y5iiijcWfd;ify;m\-t1ieiiV-readiVleks/:t:p;btrfri:-Jc>r)^eyjcr^.^'casoiirsiT:; .11' iTin.y j;>*/ .1:irit't):Wsta:ice.r.rdcr consideration oxidises v-c^irihiu^t'ipAVifej^attaiii'cdry^r^ciiriaeViddst.s imayObUm;.^ ;u:c:<:1jrit:V>t*tl.ift|r :O;'*'"--'.1:r1cture ; .this is ;b(:C;ivise: :is; Vpdrtibhs:pf.VUip;,piSi;)yicifi:f/:^^ r:I'\.S'y^bVTT\i.psOiHe^-^reft\t^st'>jfs;ct>Vrr'is,''iKji^-a^&it:VTit.,.-ycr,f-;iyolartile;'J /.'ease That.'yplaut^ at tetrij>V:fatiires \v;:idf an: ' .' woK I>alow t.in;. 1 e!iii.ion ienipiiiauire v>i. tiie.rnutpnai itsi.-tf.'. ' 1 !k'Sb''vo!rit:les oflcp..1wcb:.ne;p:iYticlc^ itnicli- final than theparehCparticieV 'H \1s' :itti r> f111ri 11'&-i.-S -;ict iir1- - "ably, shpwh ` j11 ':tHo-'rOX.'t!'; 1711e- 0f powdered -coal';which" is >l:no\yn to l:aye TOhitiics-of a hi^liIy:Vx|iias:vy . . V.TKe.'presenbirol Vniirjt nii-bbriii: xribtoi irij in; il-a. nir/.l'Sv:; ever,- may b'vin ^a'.cri .fv iiy''n:'jyrtiC>n"i lint :t -.lhrsy' be ti..:ahsorb y .much old he heat. o! cninbustioii ihat ihc tym-; ;vp`ci5.i.'Luir'"e'sjp^:t/li'O.Hbo1xi^V?vst-i_bJe':^at'e^alrWii!7?.ip'E-i1^-T-riiscria^i6yth<--;:i;j!ili" 'n*.t;ein:`)cr,vti:ie:. .0Jider. tKesci t'oriciiiiiiiis-iti*/ p:o-;.; ::7p'ij;"attipiV7^'f-r.:tlie^jnaLVne"i-t;lM'P''3S:R-;i-l?.ii" r^tistV^O}LVclr.wili-yfe^;iJrni`/ VVVhVV;h;,y:7Avy::.:v;'yf: :./Api&refore,7ihyyex{e'ibt.db;^ ; ignition" is dependent. upon ;ihci proportion ol.shch biaytcr: ..that is prescint and .'n.lsoVijj >bn ;(iit: .sipi/oiriC: ;:< n tSj of: it/ rjn<! :itbc icoibbusti blphiatferiprApiii ny/tiiis usVextimpliiipd PhpOTp L'iiVinirig:.;iv1ier<i;i'H^'p'rActice:&X'gtOfYe':3u'fititig'i'jSjpiYe.-'i'>T';rrifi'jor; iii5tf>oyt.;iiice;.' : j ::: :)v".:y;) :; "yr:.-J j" .^rV"::.vi/-' v". . The in:ia;Tiinabili1.\'r of ,i;s 'yiveii'<1 usi. is iiig]}) vr ditpancioTit. ^Jrpon jt'hfc;siy.e/bl^ Ch"e;'-pari:fcle|4^tlieir'Strufcturd;r/tl,ie'rpir<i!ience-;; ';''rj//rji3.si:be^)/gas'b;ijp^h yV?b7ijrjyani7/;ti3i;VeA\idn t ^tp'y^'liic'h'y.t iVcy v . arc electrically, chaigod. .".The' enormously jiicryns(:(i-.C'lux:-y . -t i'ical capacity .'of ;-;fnait't_icr.vy-m'';';a:.r;fiitfciy^'diyicrjcic.bf >;freq"ufeiit.^ cGji'l ri o'i-yj'C.'T.i'iSe:-of''^.jilbsiohs/cff i-boitibvistible'; /<5iiStvr->i.-f'7rlbVv-.'.'-:'.V`/yV:y.ry.:vyV.;'- Degree of Dispersion ` hi:tic i?d-n(/>Cx av present; of thorrebuidriyup Thatfeists (nijy-diyiaed f.iat'n; and :{!ip>iruct.ire cl tfeprAtjelcyviiY j>;(rt!Oi:in.r tbPsurffe cbarac: eristics.' ' pny;icc;oiii:t;. oi -the. iaci liiat1 i)<;.\vdi:i;ccl irhafeial i o;>oily .abscn bSyt 1 :(v/-^as Tii v\;!ii<j 1 ri: is.suspe: 1 tied. 11;11 rty l>c reawiiaHlfeoniPidfevKat. an -opori cellular surio.cc yvill libsorl> gas mOnfeasily than; a "iViTrt't.'i vial y yb1ds'eipgi`a'i jiocl7str.u''?:b V77IP1 -v1- y' "T'i! iV);')V rfi;'.vv':"v ..AVkch paiiich-s .possess aii open .structure: they. willd-h . .similar't;t i'iclitioris.,b<i':iv'rt:o: C; 1 c:itiiiy .-.aiiri hsove coriipletcly Hian.-pati io!c:s fepcotnpaci rrj?ikc-up.v ; fe;.p; fe Composition of the Atmosphere r.'ipi'ily. vvlsinn tho oxygon percc:rit.;ig'c. ;:>f ihciair'is reduced-., and" inVrcasefeAnlh-..thp.mai.:;istpppfe\fen. .rfeent.; 1 ; p/AP a'cei tain' rofii iyirfum fpeipohta goof iox vgerf wh ich varies. ^'i'l i'i&'') fpii'infcfplc'V.i Tiisi'-Ween'j/u'setl1;rWit iiiy/grmcli ctrinery/'- for rccVacUon:/. :.iv..tl>:ii.ai_ fo powdcie.d. ipim by leading. Hue. gaseS.iincythe.y.oiic'pf working. -V.u Yfey:'.' irVdTielihebf.fe %nirndlyV.th'6'j-'<lt3Sty.6^-pl6Sio'tiis':'in'Ol0ipajt .(he oxygen cOiher.i.lo. lTpy^ccnf., at wbiich.'.fiip.irc c V '.v.iS.iiiipos'ibVc.. .It usfwelT known tifat =}re:intic.;::uc;it.r. -df r`c6ri>l3x;iVCii>,ie eksj;S'\iiiT.b;;vhecr|fttdiui:n:-fff:sViSJ5ensV0j,f;fjti,disfier-.:; suibPiiiereaSes thpr mnamnYabllity. p ..' p;/--" P pv; - ;-. P: 7. Tuburthe point. o5 yu:\v pf.pbssibiliiy'oi explosion ihe igii.i-. lion of ;.Ui<:. dust is pcrluips ilie most .i'.rVpor.tant; iacior. : Alctliods ..i):.. igiiiribr. can'. naighly b.: gioopC'l.".'^ thiee-; . (1} '.Sp\ruldiica!ik:-.Gnii:!,ii^!.-ioii.-~:ln l.h'e, case, yi d isf, 'this Tis"VM4ii;VIJyiclu&V(p'7s|to/.ic,pj^iecj:Vi'c/fy^th'a'Kyhiis-:>;i!t;ci2rff'tira''f.od.')i;-i.'-_; ^, (2) - lr)irinj;;y,l. /.cicbif/W.'^'l'iiis .niay. .caiiso .'ex]dpsions .be-: CH'.isij oi' i.i.e ease ul .oxidriti011.';;>f-1i1ftny;fp:sti.i;>!Khowever,; l.iic fact t.liat {hc.iica! oi' 6xidati(iirishiyiTcn rlissipa'ii.-cV vory wrjuic'klyi'a'fteihiit ;i'sv:gev!pfrrt't6yT'rrrip;ktVs>ttii^:;ii'pet'ho.d,ryivi;trsrV?!j/i)[}/.:. ji.H'. tii',itiairils;avi)h: ihe .uxceptioiV of coal. : ' . 'iuliai'.iiiiahility ' and itlic rate of. ubnibustiun-.. afp increased . v.Oiy -i n'crsaL'sing ytii;tiTclesfd^pf.::ciisp'ci's')dnv^;:;V^iY^iLdtiitioii_:^<i'^ v Particles of osbestes x- 79 ; can bo yjasily iiiiderstocld 1!int .'.lie. siris.:U':'r: t'isc ..particie the: . moi.c :!enfiily. i!'ciui be:: niscut ao ignili'niii nipcr.'tiiirc. '. Also;, ^heing iibgibalerfbuiiihca.?) I)ie; partir.ics a;Y: closer together: ;;.arid)::b:ett.efya.bieytdicoiTiffiuiiiCate"-J1eWt fpififcy",:l.o'-ariof lierrt;: 1pcirriinist ances 1 \y.iierepsofriCy.6f;vilj e'j 'iri riieri a] s';;cx0Vie3 iiagl y; . . small. Some 0; the particles will Uyir, Brownian in. ,vtnu;ni:: 7J thcsC/Avillj^'roSt'Iy;;"fjVoil"itat'e;^iIi6yprppa.gatlpii'viif ::;fgV1t/iorij-ih': ''J'tli'e;:'cIoij'd;'V;'='j^s:li'a"s';Ai"rpad3'/:ibceiixiiitditi'ai]tjO'dVt'}ve.i4n'pi';eVfitieiyyf .'divided the dust' is: the liioii: clearly' tti'CS. itsd behaviour approach that oi;a;;;as;: In 116 case; however; !:as;'d\ist fen pi')Sc:ryc(i/t(' niunV; \'.:;!li rr -Pbloc:<y; .cxyrifi>:irb:>Ie =t6 That .oi ;.p^-j'i>tijBjmi^XYY?'p-U'--T3'hys^is^"lTP:-;tt>'-fT>'cbT<i.c:t;}tHa=t;eycn'hjtHcjTrti'6st) VmiiiiitppanitdPoi dust; Will, take a. relatively long.'iriic to pbecome. ) rigii'i_tec);r.'S:n'ci';>;b:iir au t'->wtaeil vipCsmp'a'riiolV- .vs'.i.tli -1hci ; 1:i'o'it:c.iics .Of-a gas. yVVe.ruiistYiVot forget the eohYplipVecsii; ylhjistibi'ijof.'cp'rlajftj^ p.tipiirbfirerativefe 'sio!!syhiay>(1c:Ve!pp;;a/:fiaxi!iniiri jirhssiirfcriiiitV riiayPhc ; groaterithpidhat gcmiraUAlPyn^ rfeiiiro. 7 .7;. '.. ;.7: r WMy. '.Btilia .: ;; aTh} . ijuriiV.; .;.tioh:r Influ In . inrcS; ..the: fi;. ..and [XC '.whic!:; -liai'iticWStip} yipihi< '/dripf'n;. of. bvi iln-. si Ym-r , All y''oy.erai ; .i:i;i:n.c.: 'A'rhlatiy; '..'duaj hj ,si;-.i-:, c! ...Ipvoces, ":Mif "(ii -. sVispen . 'ii.iligl' \ rc Ayl iich/ highly,, hecoiin; ratio of 0./5 Veil' .piintigsi arsenic 'virile i! 1. felatiVe: theirroS.V ypjiHcr/b paissagc; i.lVo'usiiiv 39 ixisti .-in a as m /^UV.iV diy.in Ictely pishes luted varies^ iai.iie'. rincvy . fPHie;. .inat c;. itiiirti;: .'losion..' i.'ori d'Aj '.ispbf-;. yigny ;acibr';-. . UVr Otitis :ed. a pphbeT Veyrii'V I-very ';uii dii' :'Tv/n</tjstrj aITGh:emi sr;::-Dec:e'ni t pir,(/ 939- : ;; i ^$yEkr!riiM-}'lgKitiot!.-'ic-;:VCiciki<s-''-:\vUir ; Laws ' of ''' v3yCr;jy.:T':^.;^iv-'dr':Vv ;Va; -: y y;y-a y y ;yy .yyy v ^1 ; - '' yTHp.Tisk.'of'dnsT hirT Tipim : !-rlVi: ini?; t'.years; xluo'sys!Vrnai:c\scieufih<; investiga- ^;ry;\ti^iSj';a'ny^Styrc1yd:a:y d- Influence of Air-Borne Matter on Health r- > In TherybaT )700/;K^^ published':a/. thesis \vhich 1 /ivVid^VejfcSlieclv-:;9rjieyi3i sfiiises ^o'iE /TTffdf-SiVieri ij//:/:'Tiyis"--\V4Lsfrp'erhii^ ;itile'Lfirs b jffi bYpifgh'piriyVist i gaidofiy;:':<5riy'-pp!9 * on.a 1";-d is.ea.sev -..^'aayjapSi=!t1ic\^fprerunWexi/p'r:;f:Jre_;Stiitdvanci"y-ix>ilAy-i^\JnrX"^*:.lidy'i":.l;^j''' " which we have Teen-abb: .to rblcyiiucyiuiiiTniniinisi::;the dust' ./:: =.-;;;Si tidy .ob the. effects, ru`: (iH-s'y.iinpn.' itics hns.Jed.' xi-.odorn d^d'';'J?yrjpiyvioriVjtbr.be'Hfevtr;-^tltatV;tHfeyiin"4aTcls^n\',y'ust7latlcfi'a'#iit''/!a.re;; TyTdependiVhtyph'vtliepfpfe^ //'.:.' (1)..'Hiu'cohc.vtii: afior. of .pfsitidles;in\!'iae'nir. at the.zone v-id 'rv^> Cdd>Ved:t.li i ng;>'y;;'.yy-ydd'd'>-\y/dy-Vrd:y'd\r':'>'da'c:r'iV.'/'-'i vv'-'dy :9r:dyayyd''' ..' \. . (2V Ccvhjiosition `o f: tin:'.pariIclos; wide); u. Tupt-govcrns ^i'ry'thfcl'g'HJi_pb'airt^l'^ytctijn'ejvLydd:.r:a;d^yy:'^ =J 3': i. i= -aVi'd 'a-:;.;'1 A'p r": i hV>:Mi"59':.r9t ;l:a;'J?'yVy>'.p;:ay.y-;;/;rdd';/-'y;'yyyd j ; : i'4,i T!. e: perj-a-J;o; expos iid of ;t!ie. workers. -P-'PcPdill ^duSiydiftweVfi^fi^i/diiii^eTdus^ffyinHaJed'c.ti&rfSisUYit'iy'. over; a' long period :pf/fiiPeyrvS^ijeThghl.y: : // i:ifi.:ri>jus.': wi:'tIf:; <.V(iVer.s of =; siiV',iI:r: siz<ant.1 shape : :iiay. be ,' ;Ycila t:\y-iydiArnyiyss.y'^ ir.divi- ; <.!11:iin: :111ion aiu.l.st.uit'.<1 ironn lie-point of view :6f i.du'ticlc y,;' v'Sjijfc'evyifiyrrricai.a.i'A;]ysi'sV[arict^iiciiVc^ii trit i till'/ :y!DStcttlpnip f-<3 u's't; t'n: ,a:r. is soiiieli'ni(:s;.'a''-very.'diif:Ci.d!: proiicidufo. .'.Heavy. ' /-'process diiit. vv: th j.v-hy;;ii t;a to of sc! tliiiij is cn.sjiy- v>*>><'`i'vr-.d. a';., iviu finer.1 dust,;: w!iici'. is tl-i: rf-ijl danger,'.tniiyVntn'i'a'in .in suHponsicinVndehnifelyhhPt-boing visible iij'soidc' cbiiditions 44J ,>viiic 1 ij.dyVoiticfcl-;j beiligy tra:pped 3i cyjfVc>gti-iis' arf? ` y'VpP*?<?.ii; the. viscous rhiieusbind nri;. caused t.o niove eitjicf; l.ack. t.oyi.He nosirils dr; to' ihi: throat by - tlic-ciiik, which' are-a ..multitude yai . Hairs'. 'IdsWn'g ./:.or.tini:rmsly : ih ' .rohsthrif ,'d ir'eclion; -p;9 :./ T- : v:y.c;'r:.-,:d <y;Leln'T) adnycanducted ydb! aigeaiiUmbV1'^ drd^:drdiiir ilicv bfficienr.yi'pf the' nose as ayriiftahs idf .diisf prc.icCf.ion; ;Vud riuy was kd-nd to .vary\yi_deIy; in .different; ^pfidpler'.yycVy-diighieftifcici'iTaeS ..w'erb'irepdrded iniwiiich'dlre '.finds't'/pf Mnipuri ties'jp f :'0 :-'S dp ;',i2,/TOi6rcfnsy:-^6fpyiiscc'Ky-;;dVery'. elaborate ap>::drn tiis.vised in .iVcse tcsi.s.which .lOOlc the font;, of jets d!" diist-lrrden :air being' blown iiiti); the nosti iIs ar.d expelied ;by. 1 he:' ir.ou: b>_nii. 1 it was .found that. K3 pci certf.. tif live. iVealtliy peojiU; \yho tmdiirlooki.to bn tested retained -10 per eente of .itHf; dust;' tlie y:i'fV:,ien.cy ;pf nil the dsufvj 6fcis:tindep fes'lid;a'ngi'h^';trpiM';70.;tOyf 0';^r;caii::7:hp -py. / r.'Afjer the.'nasal-cavities, itie next 'o.' thi; nainrai defenees l.'ti'e tli't; tr.iciie;'.. brbnclii and .broiK'.hiciic.s.. Tliest: also are. :"JiVied,yiwiitli'yciii'dO-'coii'st'jtfi Lly'^lslsli mgyina'a-Ti fp'cti'on any diistd^ogefhertveilIV rtit)cjis,lrpt-H 'being finriliy; expecto rated in fhi'.;.hafunit irtantter. 'This listiriliy.iietnoveb any tiust-Whir.f: 'may iiavc passed the dcfeiiecs of tlie^npstrils and jfa^a.1 :V'ca;yi t-ies;j-i.iyurfi)i er.:/ite fciricfes r;ccirtsistyo'f^y-ihcv'dirdsacs' <sf;t1i6yKinj|^\^h6sed\va'lis'ya.r;'eyiin'e'ti >\yji'fit;drist.:Vili>'sorbtti^.-"<SRiis'i ](h^oty ii;;-as1.; ipifagbCyf;Tiliese',-pli ii'gnr.yt ids;.ihti-vcmobility AviHnV ;fcxcitijd r)y\ Uinngn matter, kuch as .diisV; i>y wliicjr thf:y are abic tit rerii'.ii ::fhe fubes and; so expel'tlu: :dreit;:i inatie!. by. tJsc'r.ct ibn; e.f ihti cilia.. . . / ..:!iai:h of ihiybiontiiiioles tenninates ;r. a.group of.air sacs; ;ili`cr^y:'bcnrig^"a.bo3ifcy_iS;'pOO';'OpO' ^cVify.-tilTescjVfeacSiyiiiV/tjieV^ai'r'a'of' ihurnan^rivngsVjfepresen^ itliditdttil'air'dapacify.d.Th'e'tlvii'Pmcniltri'frie'iJiyalis'.of it.li'e sarcs ;'iV; in'.eru'ovcn. with' l.tlood vessels:.ldr; oxygen, Iransfer. , liyeoiriparing part :cle size :\vitli f it.-. sizcnoV Iii jig pass.ittics'; it .is -found I ii;it:.t he stiiallest'tubes /ue iii tlie.iegifm 'of 50(1 t!|icrbris'dirimetf:r flhti (lianveic.r ol ii-drhssny.dcc.r's pin),' but the niedicid preifessirtn lia vel sivpwVi'...th.n.t;pafficfes'larg^ Hl.tnicrprly-dintiVefcn' .(the diiihteter. bf-:a pa!ticUyof pollen). ;Vird yery;seldom rlojVn'ddn' -Hi(v-h'lyeoli'/pf/tlfeiitir/sdcsi'-b'iV/;;.iV;p; >- .Tlie' ctVuir.'.irison;;slio\vas . the . oltici^ .(1 it-bjViscotis 'baffleSddtd rtlie'.injiriyycla'arigesyoifr djfi;<li"onywl'iyefi-;di`cdiib'iin<i'. M;; the d'^pi.iratpry J-ky Stbin pTbv ;T^ T idtiri itg:.tl leriiTrcirri;f.lae;point;:<Vf-.y1cw;of ,tlie cffecti Boiler-flue grit.x 79 .Glass ppwdcfrx J? i y" v.-. / - A:.'coi;t:iuV: proportion . of ;'dhst dbrbathed.->:s swriiU.wed : 1. : \yh:ch;..if liotTif: ayiwisqnnus/Cf dnfecmhk'natiire, Is- not ' -' 1iigH lv or perri; iiiten t1y dangerous^ tcco-ny violciulyls'ick i.f itdpis'pertain rJiaiaiidyrifLics '. ;TI::i;.i iSiifat"ifjco'fdxJtfst\swall6^.fecI--:yfr:EiSV:tje't0ifrnJniid ib.y d^eiiidahrt.ld :bey" : 0;7^ 'the-1t>tai yjijant:*>' bWi'ritVied. s\y:iUowfd;i irn- 'y/;l-Vuritie`fi 'i ly' cey-lyiin rclnssics: 61: a i tytpriie'.rri ^'ttei'/j'suc'h afiS ;lt;acl; / ;>cbm p.W'i.idi.sridV i)i e;,fndigtV'ddiig<irS3 uki v f.-wliily ila' i^-.!'cyiVK,g.* ;>aysiii'y:to (liedy*=pi:;ntorV iiystiiiiV is of : bpreiktiyplybsmali'lda'ngcvyPippPbT^^^ : - The lirstdiny o impurities is-, j tlii; iidse, in 'whiclr uirtje particlcsdiip u:ajjpc iDViStnpihcs ')..l^Sk)i:p'yn<>sekawh ihh'yi'sd`di v'k^ ;a ^Cs'coi&s^ iyf i.: . passages fonhed / by : a; r.urnbur of shd ves' vif. bone' \vi l h > niousiiiidsdid; glands'-i.ir prdducir.g; rr.iic'.is.k :lv:nr;r particles'-- .oii 'health, .'dnsb'.ca'n.be divided into' the -'three; classes : atiirnrvl, 'vegetrible. rihd huneral.-' - .. h i ; V.'-..'. V'/.V T ' ihlveycla'ss fle'astrifonrid.tin industry ahcl. is perha jis the iiidst l.'arrnlcs's.. iTlie' ihaih'danger y/ith dust rd'this type ..is: anl.hrax/.cvliicir is hot '.if a respiriitivry' 442 The Industrial Chemist. December, 1939 nature, but is, however, classed as an industrial disease. The principal varieties of animal dust are essentially of relatively large dimensions and do not pass the first natural line of defence. The continual effort to clear away these particles is the cause of catarrh (t.e., inflammation of the covering membrane of the upper cavities, nose, larynx and windpipe). Vegetable Dust.--Under this comes wood dust, which is, along with others, capable of causing asthma. It is found that asthma is peculiar to vegetable dusts, and the reason for it is very difficult to ascertain. Various theories are put forward of which the following is the most likely. In contrast to mineral dust, these particles are soft and are not natural irritants. They aggregate into pulpy masses with mucus and moisture. It is highly probable that this pulpy mass blocks the smaller air tubes. This, in turn, reduces the surface area offered by the lungs for the transfer of oxygen to the blood, and the affected person is obliged to gasp in an attempt to get more air. Mineral Dust.--Particles of this character are the most dangerous. They do actual physical damage to the lung structure. The widely-varied effect of particles of similar shape and size, but of different materials is proof that degree of sharpness is no dependable guide to the influence on health. The death rate among emery, carborundum and glass workers is not excessive. Mineral dusts composed mainly of calcium carbonate are not highly dangerous, but those containing a proportion of free lime tend to be chemically irritant. Lime is believed to have been the cause of pneumonia epidemics amongst basic slag workers. These dusts which are chemically irritant, are really safer in industrial processes than those which are non-irritant, as they arc sufficiently unpleasant to make workers take precautions to prevent inhaling them. Silicosis This is the worst of respiratory diseases caused by air borne impurities. Certain siliceous rock in the course of blasting or drilling or grinding give rise to vast quantities of extremely fine dust, and it is this extraordinarily minute particle size coupled with the composition of the material which is the source of danger. It has been shown by Gardner that the phagocytic cells behave in an absolutely different manner in the presence of certain siliceous materials from that shown toward other types of dust. This siliceous matter is soon absorbed by the phagocytes and appears to accelerate the migration of the cells ; this is probably natural reaction to the extra effort required to remove the matter thoroughly. Then it seems the cells arc killed, and aggregate into lumps around which a fibrous growth forms. In time, which is usually a period of years, this condition is general throughout the lungs and is known as silicosis. The lung tissues in this damaged and inflamed state is very easily attacked by the bacteria of tuberculosis, whose size is 0-5 microns wide by 2 to 6 microns long, and this is the final stage of destruc tion. Dr. William R. Jones has done very valuable research work in the elimination of this terrible disease, and has led to methods of clearing the air from dangerous dust at the zone of breathing. In reviewing means at present available in mines for checking silicosis three methods may be mentioned. The first, the use of water when drilling ; secondly, well-directed and efficient ventilation ; and thirdly, regulation times for blasting. Wet drilling has brought about an enormous decrease in miners' silicosis and practically eliminated what is medi cally known as third stage silicosis. Scientific investigation has shown that wet drilling does materially allay the dust. but, where the dust has a high silica content, the concentra tion of dust and air is still highly hazardous. The main drawback with wet drilling is the disposal of the dust-laden water, because water droplets with entrained dust, often evaporate with the heat of the air, and leave the dust par ticles suspended. In spite of the fact that the rate of evaporation decreases when the relative humidity is in creased, it has been proved that with a relative humidity as high as 90 per cent., droplets of 100 microns disappear before falling 6 ft. A further disadvantage of the use of water while drilling and wetting walls of mine galleries is that, in hot deep mines, a humidification of the air results which almost reaches 100 per cent. A condition such as this is extremely conducive to tubercular infection when combined with the high temperature of deep mines. Importance of Ventilation. Ventilation in conjunction with efficient air filters is perhaps the greatest factor in health in mines and this also applies to factories. With double and treble shift blasting, as is now the custom, an enormous amount of dust is created in mine working and, as this should be removed on account of explosive, as well as health hazards, it is a matter for engineers to decide whether it is better to extract air or to provide a forced draught ; but by either method, ventilation is now regarded as the most efficient and important means in use to-day of ridding the air of fine dust and so preventing dangerous concentrations. It must be remembered that these considerations apply to all industrial processes. Dust traps used in mining appear to be still on trial, but several specialists in this type of dust control work have obtained very encouraging results. Absolute protection against air-borne impurities is often very difficult to provide, and an accurate scientific com prehension of the various factors which influence and cause any type of hazard for the workers in industry is vital. Industrial administration must strive to reach a point where these hazards are negligible. Considerable advances have been made during the last decade in the fight against the dust danger in industrial plants, both above the ground and below. Dust-contami nated air still, however, occasions serious loss of working efficiency, damages our health, industrial equipment and materials in process. (For permission to reproduce the photographs illustrating this article we are indebted to the Sturtevant Engineering Co. Ltd.) Nomenclature . c = Velocity in cm./sec. C = Velocity in ft. /min. d = Dia. of particle in cm. D = Dia. of particle in microns g n 981 cm./sec./sec. acceleration n = Viscosity of air in poises = 1,814 X 10-' for air at 70 I'- 10- cm. (mean free path of gas molecules) r -- Radius of particle in cm. S, = Density of particle S, = Density of air A = Distance of motion in time t N = Number of gas molecules in 1 mol. 606 X 10" R = Gas constant 8.316 X 107 Brownian ' movement T = Absolute temperature A1 = Surface area K = Constant k = Constant Specific surface W = Weight t = Time H -- Gas viscosity Q = Constant U -- Maximum angular distance V = Tangential gas velocity Centrifugal separation Y = Angular velocity of gas and entrained particles Z = Radius of gas path The w. Co. 1 W. 1 Limite N. 1- Co. 1' n. j Fire P: Sir I Prof F.. I of Mat Effects Office. Pcrr Co. Ini Hari Materi .Proc exxv Indi EN> of th are gi Tw< Applii prefre combi succes no de place which ageing more : coat in superi out th appea The manm doubh acetat accoui Fac 939 centra . I'.rain;. ; ,;1 -lii'Um; - | 'oiten {. 1 ate 0[ j ' r'-r.i- t deep ;y -71 almost/ ; '.-/I reineiy 7-7/' ith thy ' iteiT/isy/-;-/: :iis- afso//7/7 asting; 1' 4 .hisi is j -ved oh-/. I 'matii r . facbair/Ty/"]; iicthoVi^'vf-sS .nt/ahd.yy/.'T !: of .rli"n<5a.: 7: 71 t-Jliti s t-'. i f.;: n -.ttrial; M Avoriy// ' : is often- ., 7; :sc;;cqin-;v;:r:7 d cause Ac point/l..' ;; lie r 1ast ; 7. dustria! /ontami--: .vorking 7-. i nt and; ... - The Industrial Chemist,'December, .1939 443 Bibliography V>t6st'.;i.pieces' raft cr;'a.H 6wi win oris CSuri .: \ve!e;7hei:;se;i.;i:d. by mean's of biinincti cn dd. nangecl Clips' : :i-7c6n tainingiiiib's6'r!Mit;,(aii h5>dfq'i,is''c.oppor;.:s til pbatb.prjsilicd.;: ; -/.W.'-j't'lj',(vi bbs; .v':T hc^D ii57tyff ii?/A rd i ti.1 i\d list ry ; y ry/l7 nuist:. yfJ'i'm tiidV. / 1 $25.i'/oy':yJ ;'' rviN ^Ji '-CoKci'n dttid'AyGVRusE^^^ f.\;. :.gei;.' iThcy-were .wcig!icd;. ar.d exposed io;. 100. i>(ir..'ct'i!t.;.i - ..hliiiiiolit y,.h!;.uh. jid11iitgr: 11pLa'moist.Hro gracTi.'nt -!>qt wegtV trhc ; two sides-bfahe film.. .^joisi.;ire,passipf,MhrdiigH wa's cletei;-...- n.Tic.lV:l-rT-\I~fH-lyrovi-nrt'tiOtVdi . mined cybyt rcweigliing .at intervals 1 of;:.time. i - Nornlal 7 -Firti JVot&'tfoVv AssociWup^^^^ ;;rSir Tljlipirivas' 0?irV:V,r3>i3c:ascii'.^>f 'Occupn't!^^^ ./i /; :S-\ rr'^P_r6{ '1Cd 11i hW'-r;.:: i Vroy ` t (i res; v :,-i Pii liI tc: H ci ?i| ti\,1915r'.-' ; . celluiose jac'|ucrs arc good witli rvspcct-to.i-noisti.irc prpbfing / vp:fcutiijt;-wilIfl>e:jlsee-h;iLjltatt,-'fclre/^MiyifV^tion,".iacq\rariisrsiC-tf>fcriqti;-jp;; Tvc ^KTacJcTiti' ? aricl JJ1i cicl lp.toiiV-,V-:V ft.cj>ori.:]on*tlit:ACSj*ifcl1 rty .hiapprqxiinate'ly'iiaivu^^ rb'i'te:qf.'penctrati6h7thi *7c>f `iVi'ixtei*i aI s:rtncl\ <7.1caKi ri F :'C^v>ti n k *\v H:?ppci \1:1'<ofort;ii6cj1 p -t:1Vo ^ that,.. iii actual tliickness,: its filr:; is';ihout.ptifi-lbiir'tii:that . 'ItVre/ctV-of-Oust/ThhiUati'dn'-HipoYirflui^WoTlVbfs.-y.-r' MdlMXShit.ioviery v y(>mce7;>:i' v;v7 : /r%-lPc'rry,7::caj vpngi iid^rs H i 11/-Tioo '// of.;'itbe-:;J;or tli6tlo'xJ /iiifiterifl.1 ^rtcYud ii1g:Vpl`iern icaiVJiirui :.:?-J>1i'ysic;aY jt'cpj'oj*eCr'ti^s't<-a htlyCll ie r- 7Co^-"I nc-^-;: i7p f' .iytcfiitip'psition't-pf Ktlt'ev'thinnet'sifo'r-tHtito /y Haibhl vHey.wonrid; iWf^rvs u /'Materia!s.7S;.'./7u^ i v-cj f /t:K6 pTncWKs'^ t y". 7dr.q-i;Ho\imdh':nt'iblV'57777;.7-;.::'77;6;-7.:6'V;;,.7y;7;:.6-\.-'!?i7:Vl ,7'./.7 ;/:;7-Voccc^(?i/;ri;Vy'yH : .cxxvV't -`I rrlS:l-'r; -V'Vr::v-: i?r-V';.:j^ -.-- -V.^:'7".!^:/-7 l Stoved Glyptal Varnish . --The other, resuit, of npte: concerns tlici stoviid synthetic'. '. /glyptal yaniish'p.; VViiilc on untreated surfaces this Tailed ENAMELLING ZINC ALLOY DIE- . /complctciy - by; srdtehing \v;it!ii:i ;:fotir weeks of huniidity ; ; ..test ,/ on'.-.shot:-' blasted furnaces ..it did 'not. deteriorate, iiri ;. CAST! N G S y / ;:: -./}{Cphitniied jrem ip'?vf37) :::,;HardneM.:dr;adlT^.siqiidrf..^/-T2-fnpdrithsl/tesT/p6ri6d;/al'tli6,pJfli;.''; .'at ilarbei'.ed.ifi colour considerably:. ;-'. . 7 -. V i :.. of. the: media/.used for thry.stoved yihur.'ir.iiim /finishes' / -. Zinc alloy'. die-casti:;gs are' being -ailopted Awidely in; faieygiyeniin'p'AKle^i-d-Xyy7y/y7yy7/7yy7//77/y//7y-;-y; .. engineering indiist.r.ifis.; .-Accuracy of.-reprodiictiqn: by/tlie '.i7\a).7./tlHir7specif.d/.tcsi riwults 7dre dvoidiiy of ' tioto.'. ' tlie :c;tstinj5; prpciiss; rar.g^ of alhiy.V to. stiip.varibus/iieeds, . /Ap:)liedr:t:q; zihir! hrticics without. chemic.il ' dr/ ii'.eclianical .. -iiH-xpenSiycness. / rapaVlity 7.;f fabileati(>it:: / t lidsfi .factors /.prfctr&afrhenty.iicle^ .:ensiirc tlic-advancc/of: their popiiiarit.y.'aiid tiiility.". . Tlie; combination .cciitilosq/glypiri! .viirietyd uir:. dried,. proved ..automobile-; indiislf'y'/ for . do'rfr: iiat/diesp/hithp `brackets. . /successful /7C)\r"thc/] i ;months' iHuimdifyftesM 7dasn'/iift ir.gsi t iidiatbr.sbrhanients, steering .vvhcels, iT'c; ' no; cieteriora/ion/ l iiis is'interestiny; :heC;iuse. iin f hi: first. ' ,;/aiit6matic;.slpt:;'rn'acltinepartYi;-7:.d6mi;Stic :fittiiigs;7handles,:./j place ihTatcrirds'of this nature; give .exceedingly, thin - rilins'. . -curtain .-.accessories;, ./refrigerarbr andi. .vacuum . cleaner. .wjiicIf- '.are y/yfery/ a'diVefeitt-yaiid);shpwr.^qdd^ //conipioneiits'/'.:,W^illil^/m'acHin6r.y;;^.,clocks 7.e1ectVicci1 .'corn'-;.- ageing.' . Secondly , these .i.h:n lacquer, films. are .nulrkedly ' 7poiieiits ; cine. .]irojt:ctOr /iicnis ,. office.- er|tiij:'nient;: this ' ,i:iip'redfh'perm'cab]e/tbmloi5tu^ iexiended .range illustrates ihmr hH-<e:tcliing j-)oSsibiliti(:s-. ' coatings, of .tl-iy iirti^ !.ici;ji'icios/.. This \. y/ipon'sc^'ii.tAitTy; 77Tfic|7:7pATn tTn^;7:ahiTAr;en^meiniigd::7p>r6T31erti^ ;7 saqierior/nlOisture: .proofing- property, /-tvbich': again ; fears asscciated .with,-zinc alloys arc-likely to aionfrCuif industrial . 6i.it the.'theorics/pi.it' forwiinj. ^ the figure ; ./cheniists ii; ihriiijr :/prmres ; ./tlK.isc to.wltom/the fech'n.oiogy.r ;a'ppcarjng;cn;:p7:.436 7.0f ..finisliiiig./is. a/fixlbtimgr^uclyvTtibd^r/^ithi^li^ it is yTfeciit'^ygiVeh;-L'hi^reirtywgref;tdgriyfeci at-ifi: 'Ifflie-v'f61Lowirtgfrf' ;only..one bt ;many chemical processes iri .engineering, as fmahner.y://resfs'^ere,'.m'aiil{i':Cn,;''i;hb:,tW6'{ypes''pit lacquer 'in "well as. those'-, connected, with ./pai.iit. ', manufacture, -itself.. ifou bit:.. t hicktiesses/a ppl ied by .Spray/. t o: 6 000$ :itV./celh) lose.:. Goiisequcnt!y'. the- .foregoing; -brietly though it tleaji' with :' aci;tritc.:.:iliii. : dl'h'.i; latter, yvna..'sclooted ' as.y.thi: base oil . t he subjectshou ld . /prfVve interest mg '-and. it is - hoped,' / ac.count;.of its higii-.ii-.oiSf '.ir.e pernieabijity.'properries; yTli'e/ infornuaive. .. :-- :':-7 ::7 7-.77y:7i7..d/T'./T/'y-vA-t-V:.77;,''7 /itr/dingy..//! Factory Lighting Installation ./.neeting-y-y./ ttyo/lyfyy.i- A part of-tfie packciting lwll in ^ tfie-/,neyvdrys:'fyb(Jilding 'pfpi[ Boots Pure:. Drug Co:..Ltd. ; -195:.:. Benjam i n - S ad f l ux.. R. L. M.: / : .reflectors id re,7ri sialic d 200 watt i:lamps ;. giving an . excellent . 'distribution;fpF'slighi:}?oVeY'r;tht::;;; ii;:;. Kcdnieyofs -///; - "A\; -.r.'.sl 6Wma;n:.; .vcmenC ;pecific/'-/.y 'urfacc.'/T; ':itrifu(ar rViVraiio'iV' 444 The Industrial Chemist, December, 1939 Th A Rotary Kiln Lime Plant Installation at Abadan Sea Shells as a Raw Material THE burning of lime in rotary kilns is a well-established practice, but a recent installation by Edgar Allen & Co. Rotary Kiln A rotating table feeder under the bin extracts the raw Ltd., for the Anglo-Iranian Oil Co. Ltd., at their refinery shells and feeds them at the required rate into the rotary at Abadan is of particular interest on account of the kiln through an inclined pipe. The kiln is a steel tube unusual raw material--sea shells--which the plant is lined with firebricks, and is slightly inclined. It rotates designed to utilize. Abadan is situated on the iiver slowly on two sets of rollers and bedplates, being driven Shatt-al-Arab, which is the confluent of the Tigris and the Euphrates, about 40 miles north east of the Persian Gulf. The plant was installed for the purpose of providing by a variable speed motor. The raw shells fed in gravitate slowly to the discharge end as a result of the inclination and rotation of the kiln, and the hot combustion gases milk of lime for the oil refinery and also lime for building from the firing equipment, which is fitted at the lower end, purposes. travel in the opposite direction, gradually heating the shells Raw Material to the calcining temperature. The inside of the kiln is fitted with a lining of refractory The sea shells arc deposited in large quantities on the material and an insulating lining between the steel shell shore of the Persian Gulf. They are brought to the works and refractory lining. For European conditions an in barges. The size of the shells varies between about insulation is recommended principally for the purpose of 2 in. and \ in., and even smaller. On a sieving test it was reducing the heat lost by radiation and thus for fuel found that approximately 40 per cent, passed through a economy, but for climates such as at Abadan, where the sieve with | in. square holes. shade temperature in the summer reaches 125 F., it is also The chemical analysis proves that the shells are fairly essential for the. preservation of the plant. pure calcium carbonate. The composition is :-- The waste gases from the kiln pass through a brick dust Loss on ignition Per cent. .. 43-03 chamber and through a cyclone dust collector, and are exhausted into the atmosphere by an induced draught fan. Silica .. .. Alumina .. Ferric oxide .. Lime .. .. Magnesia .. Difference .. .. I-10 } 0-74 .. 53-00 .. 1-56 .. 0-57 The fan is driven by a variable speed motor for the purpose of adjusting the speed in accordance with the volume of gas to be handled. Oil Firing Equipment Total .. .. 100-000 Being located at an oil refinery, the kiln is, of course, fired with oil fuel. This fuel lends itself exceptionally well The shells burnt in a' rotary kiln arc hydrated and the hydrate freed from nibs and impurities by passing it through an air separator. The arrangement of the lime burning plant, the hydrator and the air separator is illustrated in Fig. 1. The raw shells arc filled into a receiving hopper and are lifted by means of an elevator into an overhead storage bin placed over the kiln feeder. The bin is filled every morning in 2 to 3 hours and has sufficient capacity to supply the kiln with raw material for 24 hours. for burning lime because the firing is under close control, no impurity is introduced into the lime, and the calcining temperature can be maintained between very narrow limits. The oil is atomised in the burner by compressed air, which may be considered extravagant, but ensures very thorough atomisation besides being reliable, particularly when attended to by unskilled labour. The oil used has a viscosity of 140 secs. Redwood No. 1 at 100 F. and a specific gravity of 0 913, so that heating is not necessary. The firing equipment comprises the burner, an oil Fig. I--Elevation showing the arrangement of lime-burning plant, hydrator and air separator pump with filters on the suction and delivery sides and an air compressor, control valves and gauges. MWvertical Elevator Burnt Shells Storage Bin Extracting Scre* htilmc condenser] Hrorator 1 )p5 -- Rotary. .'MR- -- "Tt --r Tray Conveyor r~ ^r Hydi Th is th< mean for tl the q light; aboul mach shells hydre with hydra are re passe: addec in it j waslu water The conta be inc if the fore, nibs a The which veyor Milk The about practi kiln p slurry plant, furthe The cent. 1 concre pipes ample water the sir In o is add' >39 2 raw otary tube states Iriven vitate lation gases r end, shells ictory t shell is an ose of r fuel re the is also k dust id are nt fan. urpose of gas :ourse, ly well ontrol, lcining narrow pressed :s very cularly 1 used 00 F. is not an oil and an The Industrial Chemist, December, 1939 445 Hydrating Plant The quicklime, having been discharged from the kiln, is then conveyed on a steel tray conveyor and lifted by means of a bucket elevator into a hopper over the feeder for the hydrator. The duty of the hydrator is to convert the quicklime or calcium oxide into hydrated lime, a very light and fine powder. This conversion is effected by adding about 30 per cent, of water to the quicklime. The hydrating machine is designed to the Schulthess patents. The burnt shells are extracted from the hopper and fed into the hydrator by an automatic table feeder, and are moistened with a portion of the hydrating water in the preliminary hydrating compartment. Any hard lumps and impurities are retained in this compartment. The partly slaked lime passes into the second compartment, where more water is added. The steam created and the very fine dust suspended in it pass through a condenser into the atmosphere and are washed in it before being discharged. The washing water is the water used in the hydrator. The grading analysis of the hydrate showed that it contained a few nibs and some impurities. These would be inconvenient in the milk of lime plant and objectionable if the lime were used for building purposes. It was, there fore, decided to instal an air separator for removing the nibs and impurities. The pure hydrate is elevated into a storage bin from which it is withdrawn as required by an extracting con veyor. Milk of Lime Plant The milk of lime plant is erected in the oil refinery about three miles distant for the rotary kiln. It was not practicable to pump the milk of lime this distance from the kiln plant to the refinery, but it was decided to make a lime slurry containing about 40 per cent, of water at the kiln plant, and transport it to the refinery in tank wagons for further treatment. The tank wagons, having arrived at the plant with 40 per cent, lime slurry, are emptied, and the slurry is run into two concrete mixers equipped with mechanical stirrers and pipes for agitating by compressed air. The mixers are of ample size so that if any irregularity in the percentage of water in the various tank wagons exists, the consistency of the slurry in the mixers is practically uniform. In order to produce 10 per cent, milk of lime, more water is added to the 40 per cent, slurry. For this purpose it is pumped by a centrifugal pump into a measuring tank with Vnotch and overflow for surplus slurry. The V-notch is adjustable and allows a determined volume of slurry to flow out, and any surplus is returned to the mixers. Water is added in metered quantity to the slurry flowing over the V-notch from the measuring tank to make 10 per cent, milk of lime, and both liquids are run into a Clark's slurry separator which retains any im purities that may have found its way into the slurry and at the same time effects thorough mixing. The finished 10 per cent, milk of lime is run into a storage tank, where it is kept in suspension by mechanical stirring. The plant is well equipped with instruments for the control of the temperature, where this is neces sary. Unfortunately, there is no instrument on the market by means of which the calcining temperature can be indicated or recorded. The method adopted at Abadan is to measure the burnt lime as it falls out of the kiln by means of an optical pyrometer through a hole in the discharge hood. This temperature is in fairly close relationship to the calcining temperature, and the fuel supply is adjusted according to the reading. A great asset to the plant is the oil for firing. The ease of temperature control, and the speed with which adjustments can be made, make it possible to produce continuously well burnt lime of uniform quality, and it has been proved that a temperature main tained within narrow limits is necessary for maximum conversion of the lime to soluble hydrate. Such close temperature control is only possible in a rotary kiln and with oil firing this is comparatively easy. Another adjust able factor in the calcining process is the speed of rotation of the kiln, although alterations in this direction are not often necessary. Control of Hydration The hydrating process also is controlled by temperature of the hydrate discharged from the machine. It has been found that if the water supply be adjusted in accordance with the temperature of the hydrate discharged, the percentage of water is about correct. Normally the temperature is about 100 C. One foreman is in charge of the plant and a staff engineer calls once every shift to take readings of the various instruments. Close watch is also kept on the kiln waste gases, the temperature is measured, and the chemical analysis checked for carbon dioxide and oxygen. The least volume of excess air, which would increase the fuel consumption, is allowed to enter the kiln. DETECTION OF ANILINE VAPOUR IN the series of leaflets describing methods of detecting toxic gases in industry, a new publication is No. 11, which describes a method whereby concentrations of aniline vapour ranging from 1 part in 5,000 to 1 part in 200,000 may rapidly be estimated by a refinement of the bleaching powder test. This test has been made quantitative by comparing the colours obtained at low concentrations with a series of standard colours prepared from a dye. This leaflet, and a pamphlet describing the complete series of gases and vapours to be covered, can be obtained from the Department of Scientific and Industrial Research.