KESEARCHES UPOlSr THE CHEMICAL PROPERTIES OF GASES. 195 



view to its decomposition by hydrochloric acid which liberates the pure acetylene, 

 great care is necessary to avoid exposure to the air (Keyser, Am. Cliem. Jr., 1892, 

 p. 285). According to Berthelot, the copper compound is vinyl oxide in which 

 copper has replaced hydrogen. 



H H 



Cu I I Cu 



\ 1 I / 



C = C— 0— c = c 



\ 



Cu Cu {Ball Soc. Chim (2), V, p. 191). 



According to Keyser, the copper and silver compounds are CU2C2 and Ag2C2. 



Silver nitrate is probably the most sensitive reagent tried. Moreover, as the 

 silver compound does not appear to be susceptible to oxidation, it may be used in 

 testing for acetylene in the presence of air or oxygen, while the copper compound, 

 on account of its strong tendency to undergo oxidation, is far less easily recognized 

 in deeply colored copper solution. Potassium permanganate in concentrated sul- 

 phuric acid, calcium hypobromite and osmic acid are the only reagents which cause 

 direct oxidation in the cold of acetylene to carbon dioxide. As an unsaturated 

 hydrocarbon, its indifference towards iodine solution was somewhat unexpected in 

 view of the avidity of isobutylene for iodine (see p. 193). 



The prompt reduction of gold chloride forms a singular contrast to the indiffer- 

 ence of platinum chloride towards acetylene. The color of the gold when precipi- 

 tated by acetylene (usually blue or blue-black) is quite different from the brownish- 

 yellow color so often observed when gold salts are reduced. 



This difference in color of the precipitated gold is probably not due to rapidity 

 of reduction. 



ALLTLBNE. 



This hydrocarbon was prepared from propylene bromide l)y the action of alco- 

 holic potash. The gas resulting was washed bj' boiling alcoholic potash solution 

 and absorbed by aramoniacal cuprous chloride. The yellow precipitate resulting 

 was washed and afterwards decomposed by hydrochloric acid, allylene being then 

 set free in a pure state. 



1. Reactions in Solution. 



REAGENTS. REACTIONS. 



Palladium chloride Dark-brown precipitate, which may be preserved with- 

 out decomposition. Closely resembles the precipi- 

 tate produced by acetylene. 



Platinum chloride Unchanged. 



Gold chloride Slowly reduced. The color of the precipitated gold is 



very dark. 



