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AHLBORG--HYDROGEN SULFIDE POISONING IN SHALE OIL INDUSTRY 249 the workers had smoked tobacco before the test. The carbon monoxide exposure is therefore slight. Moreover, in patients suffering from acute gas poisonings (described below) one did not find pathological values of COHb. Hydrogen cyanide and carbon disulfide occur in too small concentrations to cause poisonings, and the same is true for the mercaptans, the latter, by the way, being relatively innocuous ethyl and methyl mercaptans. The content of sulfur dioxide varies considerably within the plant, and this gas does not occur in the distillation gases, as will appear from table 1. Air analy ses proved that only at one place did the concentration exceed the tolerance limit for persons not accustomed to sulfur dioxide. It can therefore be excluded as an etiological factor, at least for serious poisonings. After condensation only those hydrocarbons remain which are still in gas form at the condensation temperature, i. e., hydrocarbons with less than five carbon Table 1.--The Composition of the Gases Mentioned in Chart 1 (A-H) in Percentage Gas A B O D E P G H H2S 16 28 14 25 20 0.5 0 0.5 C02 10 8 12 5 10 4 0 4.5 CO 1 1 1 0.5 1 1 01 02 0.5 0.2 0.5 0.1 0.5 0.4 0 0.5 n2 35 12 25 2 25 29 0 33 h2 16 18 28 20 20 25 cm c2m 21 1 0 27 0 24 01 C2Hg 8 0 8.5 CaHo 2L5 33 20 48 24. 1:6 17 0 Calls 3.5 33 0 CaHs 2 22 0 CgHio 2.5 28 0 Co 0.5 0 0 HCN CS2 About 50 mg./m.3 , . About 1 Gm./m.3 0 00 00 COS About 1 Gm./m.3 00 RSH About 5 Gm./m.3 00 atoms. They will form approximately a quarter of the gas piped through the plant and are (a) the paraffins methane, ethane, propane and butane and (b) the olefins ethylene,.propylene and butylene (table 1). The first two (methane, ethane) make up the main part, but they are simple asphyxiates, i. e., physiologically inert gases that act . only mechanically by excluding oxygen. Propane and butane have some anesthetic properties, but, according to Henderson and Haggard *2 (1943), there are apparently no ill effects from remaining for several hours in an atmosphere containing these gases in concentrations as high as 3 to 5 per cent, or from repeated exposure. Ethylene, propylene and butylene have anesthetic properties only at high concentrations, 60 per cent or more. The liquefied gas, named.^Gasol, contains approximately 17. per cent of pro pylene, 33 per cent of propane, 22 per cent of butylene and 28 per cent of butane; therefore the toxicity of this gas is exceedingly small, especially as compared with the usual city gas. ' N/ 2. Henderson, Y., and Haggard, H. W.: Noxious Gases and the Principles of Respiration Influencing Their Action, American Chemical Society Monograph Series, no. 35, New York, Reinhold Publishing Corporation, 1943, li 1