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American Society of Heating and Ventilating Engineers Guide, 1937 Table 1. Regain of Hygroscopic Materials Moisture Content Expressed in Per Cent of Dry Weight of the Substance at Various Relative Humidities--Temperature, 75 F CuB8F nCATTON Material Description Relative Humidtit--Per Cent Authority 10 20. 30 40 50 60 70 80 90 Cotton Sea island--roving 2.5 3.7 4.6 5.5 6.6 7.9 93 1L5 14.1 Hartehon* Cotton . Cotton American-- cloth =. Absorbent 2.6 .3.7 4.4 S3 5.9 6.8 8.1 10.0 14.3 ScMoeriog 4.8 9.0 12.5 15.7 18.5 20.8 223 243 25.8 Fuw Natural Textile Fibres Wool fiilV Tliwn Tjnwi Jute Hemp Australian merino--skein 4.7 7JO 8.9 10.8 123 14.9 17.2 19.9 23.4 Hartahon* Raw cheyennes--skein 33 S3 6.9 8.0 8.9 ia2 11.9 14.3 18.8 Schloeeiag Table doth 1.9 2.9 3.6 43 5.1 6.1 7.0 8.4 10.2 Atkinson Dry spun--yarn 3.6 5.4 63 73 8.1 8.9 9.8 11.2 13.8 Sommer Average of several grades 3.1 5.2 6.9 83 ia2 12.2 14.4 17.1 202 Storch Manila and iraqd--rope 2.7 4.7 6.0 7.2 S3 9.9 11.6 13.6 15.7 Fawn i il I t ; Rayon Viscose NitroceDu. lose Capramomum Average skrin Cellulose Acetate Fibre M. F. Newsprint Wood pulp--24% ash 4.0 5.7 6.8 7.9 9.2 10.8 12.4 14.2 16.0 Robertson 0.8 LI 1.4 1.9 2.4 3.0 3.6 43 5.3 Robertson 2.1 3.2 4.0 4.7 S3 6.1 73 8.7 106 U. 8.B. ofR Paper H. M. F. Writing White Bond Wood pulp--3% ash Rag--1% ash 3.0 4.2 5.2 6.2 73 83 9.9 11.9 14.2 U. 8. B. of S. 2.4 3.7 4.7 5.5 63 73 83 10.8 13.2 U.RB.o{R Com. Ledger Kraft Wrapping Leather 75% rag.--1% ash Coniferous Sole oak--tanned' 4 i3.2 4.2 5.0 5.6 6.2 6.9 8.1 103 13.9 U. S.B.0IS. 3.2 4.6 5.7 6.6 7.6 8.9 10.5 116 14.9 U. R B. of 8. V * 5.0 8.5 1L2 13.6 16.0 18.3 20.6 24.0 29.2 Phelpe Catgut Racquet strings 4.6 73 8.6 ia2 12.0 14.3 17.3 19.8 21.7 Fawn Mfac. Organic Glue Rubber Wood Hide Solid tire Timber (average) 3.4 4.8 5.8 6.6 7.6 9.0 10.7 1L8 12.5 Fuwa an 0.21 0.32 0.44 0.54 0.66 076 OSS 0.99 Fuwa 3.0 4.4 5.9 7.6 93 1L3 14.0 17.5 22.0 Forest P. lab. Soap White 1.9 3.8 5.7 7.6 10.0 12.9 16.1 19.8 23.8 Fuwa Tobacco Cigarette 5.4 8.6 11.0 133 16.0 193 25.0 33.5 500 Ford White Bread 0.S 1.7 3.1 43 6.2 8.5 11.1 14.5 19.0 Atkinson Crackers - 2.1 2 3.3 3.9 5.0 63 8.3 109 14.9 Atkinson Food stuffs Macaroni Flour 5.1 7.4 8.8 10.2 11.7 13./ 16.2 19.0 22.1 Atkinson 2.6 4.1 S3 63 8.0 9.9 114 15.4 19.1 Bailey Starch 2.2 3.8 5.2 6.4 7.4 83 93 106 12.7 Atkinson Gelatin 0.7 1.6 2.8 33 4.9 6.1 7.6 93 11.4 Atkinson Asbestos Fibre Finely divided ai6 0.24 0.26 032 0.41 051 062 073 084 Fuwa Sifiea Gel Mine. Inorganic Domestic Coke Materials Activated Charcoal Steam activated 5.7 9.8 12.7 15.2 17.2 18.8 202 21.5 22.6 Fuwa 0.20 0.40 0.61 0.81 1.03 1.24 1.46 1.67 1.89 Setvig 7.1 14.3 22.8 26.2 28.3 29.2 300 31.1 32.7 Fuwa Sulphuric Arid HaSO. 33.0. 41.0 47.5 52.5 57.0 61.5 67.0 73.5 82_5 Mason iCi 728 Chapter 40--Air Conditioning for Industrial Processes percentage of the total weight of material. Regain is more specific and refers only to hygroscopic moisture. It is expressed as a percentage of the bone-dry weight of material. For example, if a sample of cloth weighing 100.0 grains is dried to a constant weight of 93.0 grains, the loss in weight, or 7.0 grains, represents the weight of moisture originally contained. This expressed as a percentage of the total weight (100.0 grains) gives the moisture content or 7 per cent. The regain, which is expressed as a per- 70 centage of the bone-dry weight, is or 7.5 per cent. The use of the term regain does not necessarily imply that the material as a whole has been completely dried out and has re-absorbed moisture. In the case of certain textiles, for instance, complete drying during manu facturing is avoided as it might appreciably reduce the ability of the material to re-absorb moisture. In measuring moisture it is necessary to dry out a sample so that the loss in weight may be used as a basis for calculating the regain of the whole lot. The moisture content of an hygroscopic material at any time depends upon the nature of the material and upon the temperature and especially the relative humidity of the air to which it has been exposed. Not only do different materials acquire different percentages of moisture after prolonged exposure to a given atmosphere, but the rate of absorption or drying out varies with the nature of the material, its thickness and density. Table 1 shows the regain or hygroscopic moisture content of several organic and inorganic materials when in equilibrium at a dry-bulb tem perature of 75 F and various relative humidities. The effect of relative humidity on regain of hygroscopic substances is clearly indicated. The effect of temperature is comparatively unimportant. In the case of cotton, for instance, an increase in temperature of 10 deg has the same effect on regain as a decrease in relative humidity of one per cent. Changes in temperature do, however, affect the rate of absorption or drying. Sudden changes in temperature cause temporary fluctuations in regain even when the relative humidity remains stationary. INDUSTRIES REQUIRING AIR CONDITIONING A few of the industries in which air conditioning plays an important part and the major uses in these industries are as follows: Automobile. Drying of siccative coatings, manufacture of steel, manufacture of artificial leather, drying of rubber, manufacture of tire fabrics, cementing of inner tubes, conditioning of wooden spokes and other wooden parts, conditioning and manufacturing of all electrical windings in connection with the electrical apparatus, storage battery plates and the rubber containers. Bakery. Flour storage, yeast and ingredient storage, mixers, fermentation rooms, make-up room, proof boxes, load cooling, wrapping (including paraffin paper), cake mixing and cake icing. Brewery. Fermentation and starting rooms. Chemical. Powders (including explosives and baking powder), drying of salts of all kinds, hygroscopic compounds and drugs, glues and gelatins. Clay Products. Bricks, pottery and ceramics. Confectionery. Chocolates, bon bons, hard candy, gum drops, marshmallows, caramels, chewing gum and starch and various sugars. 729