CABBOH ANJ) TIIK HVDKOCAIM'.ONS :;C,1 



cuinstances (Berthelot, Sawitsch, Miasnikofi) the alkali takes up the 

 hydrobromic acid from C^H.^^Br, forming C, ( H 2n _ 2 . 



Acetylene is also produced in all those cases where organic sub- 

 stances are decomposed by the action of a high temperature for 

 example, by dry distillation. On this account a certain quantity is 

 always found in coal gas, and gives to it, at all events in part, its 

 peculiar smell, but the quantity of acetylene in coal gas is very small. 

 If the vapour of alcohol be passed through a heated tube a certain 

 quantity of acetylene is formed. It is also produced by the imperfect 

 combustion of olefiaiit arid marsh gas for example, if the flame of 

 coal gas has not free access to air. 49 The inner part of every flame 

 contains gases in imperfect combustion, and in them some amount 

 of acetylene. 



Acetylene, being further removed than ethylene from the limit 

 C,,H 2 ,, +2 of hydrocarbon compounds, has a still greater faculty of combi- 

 nation than is shown by olen'ant gas, and therefore can be more readily 

 separated from any mixture containing it. Actually, acetylene not only 

 combines with one and two molecules of I 2 , HI, H 2 SO 4 , C1 2 , Br 2 , 

 *kc. . . . (many other unsaturated hydrocarbons combine Avith them) but 

 also with cuprous chloride, CuCl, forming a red precipitate. If a gaseous 

 mixture containing acetylene be passed through a solution of cuprous 

 chloride (or AgNO 3 ) and ammonia water, the other gases do not com- 

 bine, but the acetylene gives a red precipitate (or gray with silver), 

 which on being struck with a hammer decomposes with an explosion. 

 This red precipitate gives off acetylene under the action of acids. 

 In this manner pure acetylene may be produced. Acetylene and its 

 homologues also readily react with corrosive sublimate, HgCl 2 (Kou- 

 cheroff, Favorsky). Acetylene burns with a very brilliant flame, which 

 is accounted for by the comparatively large amount of carbon it 

 contains. 50 



The formation and existence in nature of large masses of petroleum 

 or a mixture of liquid hydrocarbons, principally of the series C /i H 2+2 

 and C, ( H 2n is in most respects remarkable. 51 In some mountainous dis- 



49 This is easily accomplished with those gas lamps which are used in laboratories 

 and mentioned in the Introduction, page 11. In these lamps the gas is first mixed with 

 4vir in a long tube, above which it is kindled. But if it be lighted inside the pipe it does 

 not fully burn, but forms acetylene, on account of the cooling effect of the walls of the 

 metallic tube ; this is observed by the smell, and may be shown by passing the 

 issuing gas (by aid of an aspirator) into an ammoniacal solution of cuprous chloride. 



60 Amongst the homologues of acetylene, C,,H. 2W - 2 , the lowest is C 5 H 4 ; allylene, 

 CH 3 CCH, and allene, CH 2 CCH 2 , are known, but the closed structure, CH 2 (CH) 2 , is 

 unknown. 



51 The saturated hydrocarbons predominate in American petroleum, especially in 

 its more volatile parts ; in Baku naphtha the hydrocarbons of the composition C rt H 2 H form 



