196 Chemical Notices : — M. Berthelot on a New Hydrocarbon. 



law (which I have given in the Philosophical Transactions, 1859, 

 p. 768) tends to show that there cannot be any very important 

 departure from this law ; otherwise they would be detected by 

 comparing geodetic and astronomical measures of the amplitudes 

 of arcs, especially wherever those measures have been made in 

 countries free from large visible causes of disturbance, such as, 

 in this country, the Himmalayas and ocean. 



Mr. Hopkins's solution he professes only to be an approxima- 

 tion — an answer, in fact, to the question, Is the thickness of the 

 earth's crust a large or a small fraction of the radius ? The 

 consideration of the geographical features of this part of the 

 world (the largest mountain mass anywhere known lying on the 

 north, and an unbroken ocean lying to the south of Hindostan) 

 which I have brought forward, is for the same purpose, — not 

 to attempt an exact solution, but to reply to the question I have 



q uoted - J. H. Pratt. 



Calcutta, July 9, 1860. 



XXVI. Chemical Notices fi-om Foreign Journals. 

 By E. Atkinson, Ph.D., F.C.S. 



[Continued from p. 143.] 



BERTHELOT* has described a new hydrocarbon. He calls it 

 acetylene, or quadricarburetted hydrogen. It has the for- 

 mula C 4 H 2 , and is the prototype of the hydrocarbons C 2n H 2TC ~ 2 . 



Acetylene is produced whenever olefiant gas, alcohol vapour, 

 ether, aldehyde, or even wood-spirit are passed through a red- 

 hot tube. It is also formed when chloroform acts upon copper 

 at a red heat : it is contained in illuminating gas. Ether yields 

 it in largest quantity. 



In order to obtain it pure, it is formed into a compound with 

 subchloride of copper. This compound is identical with a red 

 detonating body obtained by passing the gases arising from the 

 decomposition of alcohol by the electric spark or by heat, into an 

 ammoniacal solution of subchloride of copper. It was discovered 

 by M. Quet, and examined by M.Bottger; but neither of these 

 chemists analysed the gas which is liberated when this body is 

 treated with hydrochloric acid. This gas is acetylene. 



It is a colourless gas, somewhat soluble in alcohol, with a cha- 

 racteristic disagreeable odour. It burns with a very luminous 

 fuliginous flame. Mixed with chlorine, it detonates almost in- 

 stantaneously, with deposition of carbon, even in diffused light. 

 It cannot be liquified. Its density is 0*92. Its formula, C 4 H 2 , 

 corresponds to four volumes. 



* Comptes Rendus, April 1860. Repertoire de Chimie, June 1860. 



