Document Ne76BqNJaObEya8ZXDQBgjvQ8

180 FRANK A. PATTY Solvent Methyl alcohol Ethyl alcohol rv-Propyl alcohol n-Butyl alcohol Amyl alcohol Methyl amyl alcohol Ethyl formate Ethyl acetate n-Butyl acetate Amyl acetate Ethyl propionate Furfural Acetone Butanone Pentanone Hexanone Hexone Heptanone Octanone Meaityl oxide Isophorone Ethyl ether Isopropyl ether n-Butyl ether Cellosolve Dioxane Pentane Hexane TABLE 3 Unit Refractivity Change (/AR) VaB x 10* Solvent 2.5 6.4 8.6 11.6 143 16.7 8.711.6 18.0 20.4 . 14.7 13.1 7.6 103 13.1 16.1 16.6 19.0 21.9 16.3 193 11.9 17.8 23.0 11.8 113 13.4 16.6 Heptane Octane Cymene Cyclohexane Cyclohexene Cyclohexanol Cyclohexanone Methyl cyclohexane Methyl cyclohexanone Benzene . Toluene Xylene Ethylbenzene Pyridine Chloroform Carbon tetrachloride a-Dichloroethylene Trichloroethylene Tetrachloroethylene Ethylene dichloride Propylene dichloride Dichloroethyl ether Chlorobenzene Ethyl bromide Ethylene bromide Ethyl iodide Carbon disulfide Water unit x i 193 J 22.7 "I 25.9 1 15.1 J| 14.4 .W ls-4 H 13.7 i7.5 fl 163' 1J$| 14:4-1 17.6i/ 20.4;.^ 20.1.,-Ji 12.7 a n.3 3 HA*! 103 13.7,J1 16.9,.,.J| 11.1 i3i^:S 16:9';3H! 17.5 fi^j 9.5 .af! 143jl| -0.2S The refractivity of a mixture of vapors is the sum of the refractivities of the coS ponents. Water vapor gives a negative reading and if it has not been removed-from the atmosphere to be sampled, any difference between the humidity of the atmf|| phere in which the zero point was set and the atmosphere to be sampled must'Bf measured and taken into account. j Portable Orsat The portable Orsat10 consists of a 100-ml. gas buret and four pipets: pH| containing sodium-hydroxide, one alkaline pyrogallate, one acid cuprous chloMaf solutionjwand-the*ifourth-bein^a-slow. combustion pipet for--burning-combuSti^ gases. The apparatus is suitable for the determination of carbon dioxide, oxyg nitrogen, methane, and some other combustibles, including carbon monos ldt/n^i high concentration. Concentrations of carbon monoxide high enough to be detected " W. P. Yant and L. B. Berger, U. S. Bur. Mines Miners' Circ. No. 34, 1936. jMPv SAMPLING AND ANALYSIS OF CONTAMINANTS 181 M^WniMtevice are, however, immediately dangerous to life. The limit of accuracy ft'3&!^f^|}per cent. The chief application of this device is in the analysis of the mines. 8. Combustion Devices ^(''oyYbustihle Gas Indicators. Combustible gas indicators of numerous kinds ^avaiiab||..In the majority of these instruments the atmosphere to be tested is glr^vn5.ac|TM?, a platinum filament which is heated by a dry cell. This filament u01jijrSarm of a Wheatstone bridge and is balanced before use against another in an inert atmosphere. Any combustible gas in the sample drawn Jci'n^Lne ^bat: filament is oxidized or burned catalytically, which burning results BH^S^^pffll^vtemperattire of the filament and a consequent increase in resistance eleotricity. The increase in resistance is proportional to the amount of _'l^nn?5Bl'ejgases or vapors in the sample and is measured by a meter that has a i^dflcffibyated for certain classes of vapors to give readings directly in percentage B^^Mer^fiammable limit. The sensitivity of these devices varies from the less inwb^.jMjibrated in fourths of the lower flammable limit, to the most sensitive tr^pSculi^ated to a few p.p.m. These instruments are very useful in locating and in evaluating fire and explosion termed a "benzene indicator." All of them SllllPiecked periodically against known mixtures of the vapor to be analyzed. trJ|fnMonoxide Indicators. Carbon monoxide is perhaps most satisfactorily fy drawing theTair to Be 'an"aTyzed, 'at a consfantTate, through Hopcalite, Unsitive thermocouples are located. The Hopcalite catalyzes the union of imOnSxide with oxygen to form carbon dioxide, and the heat generated by _ 'ikconverted to electrical energy by the thermopile and registered by a ^Jgbtentiometer or a millivoltmeter.11 The air to'be analyzed must be dried |||means, and must be freed of interfering combustible gases by drawing it Motivated carbon filter. Hydrogen, methanej!ahd nitrogen dioxide are Spl'emoved by this treatment and, if present, will yield high results. Jjfpitained, portable instruments embodying the above principle are availIMigse portable instruments are sometimes subject to significant errors ariations in humidity and temperature, especially .where-measurements (g^ml^are' desired. TThlia'e'difficfiVty rovff oeest+aabfvTHisnElriiiTnfgf ncnonnosftdaTniit izraeeron vreaaad^linnngos ^Jen|(i by recirculating the air through the instrument; This is especially rin|iold weather when the air to be measured is warm and the reference air jbncold, or when the reference air is suspected of containing traces of carbon '"Snipe"this-instrument is-also' subject-to altitude fluctuations,ritr is un,/imeasuring low but significant amounts of carbon monoxide in airplanes. I^ , [ K-tz, D. A. Reynolds, H. W. Frevert, and J. J. Bloomfield, V. S. Bur. Mines Tech. 1926. , Monoxide Indicator, Mine Safety Appliances Co., Pittsburgh, Pa.,