i 9 o8] CROCKER AND KNIGHT— CARNATIONS 267 



To make sure that the effect produced by ethylene was not due to 

 some impurity contained by it, parallel experiments were run with 

 ethylene derived by two different methods: (1) by heating concen- 

 trated sulfuric acid with absolute alcohol, and (2) by dropping abso- 

 lute alcohol upon phosphorous pentoxid heated to 200 C. and later 

 raised to 240 C. The ethylene derived from sulfuric acid was 

 washed by the ordinary gas burette and pipette, as described by 

 Hempel (15:34-95); first in concentrated sulfuric acid (sp. gr. 

 1.84) to remove the aldehyde, and later in 33 per cent, potassium 

 hydrate to remove the sulfur dioxid. In each case the washing was 

 continued until no further absorption occurred. The ethylene 

 derived from phosphorous pentoxid was washed similarly, and in addi- 

 tion in copper sulfate (sulfuric acid solution described by Hempel, 

 p. 316) for absorption of phosphene, if any should be present. 

 Various samples of the ethylene derived in this way were analyzed. 

 Bromin and fuming sulfuric acid absorbed 96-98 per cent. The 

 unabsorbed portion proved to be air, coming from the generator 

 chamber. The gases thus derived were diluted with air to form 

 mixtures containing 2 per cent, ethylene. The toxicity of the two 

 mixtures was equal. 



In discussing the composition of illuminating gas we can hardly 

 do better than quote a paragraph from Smith's (16) General chem- 

 istry for colleges: 



The illuminating gas in Europe, and in many of the smaller cities of the 

 United States, is usually coal gas; while in the larger cities of America it is almost 

 always made from water gas. Coal gas is obtained by the destructive distillation 

 of soft coal, and is freed from ammonia and tar by washing and cooling, and from 

 hydrogen sulfid and carbon dioxid by passage through layers of slaked lime. 

 The water gas, made by the action of steam upon anthracite or coke, being com- 

 posed of carbon monoxid and hydrogen, has no illuminating power. It is there- 

 fore "carburetted," that is, mixed with hydrocarbons, by passage through a 

 cylindrical structure filled with white-hot firebrick, upon which falls a small 

 stream of high-boiling petroleum. The relatively involatile hydrocarbons of 

 which the oil consists are thus decomposed ("cracked"), and gaseous sub- 

 stances of high illuminating power are produced. The following table shows 

 the composition of each of these kinds of gas, together with that of oil 

 gas (Pintsch's) which is composed entirely of the products from "crack- 

 ing" oil: 



