1879.1 Professor Roscoe on a Ncic Chemical Industry. 51 



WEEKLY EVENING MEETING, 



Friday, February 21, 1879. 



William Spottiswoode, Esq. M.A. D.C.L. Pros. R.S. Vice-President, 



in the Chair. 



Professor Roscoe, LL.D. F.R.S. 



A New Chemical Industry, established by M. Camille Vincent. 



" After I had made the discovery of the marine acid air, which the 

 vapour of spirit of salt may properly enough be called, it occui-red to 

 me that, by a process similar to that by which this acid air is expelled 

 from the spirit of salt, an alkaline air might be expelled from sub- 

 stances containing the volatile alkali. Accordingly I procured some 

 volatile spirit of sal-ammoniac, and having put it into a thin phial 

 and heated it with the flame of a candle, I presently found that a 

 great quantity of vapour was discharged from it, and being received 

 into a basin of quicksilver it continued in the form of a transparent 

 and permanent air, not at all condensed by cold." These words, written 

 by Joseph Priestley rather more than one hundred years ago, describe 

 the experiment by which ammonia was first obtained in the gaseous 

 state. 



Unacquainted with the composition of this alkaline air, Priestley 

 showed that it increased in volume when electric sparks are passed 

 through it, or when the alkaline air (ammonia) is heated the residue 

 consists of inflammable air (hydrogen). 



Berthollet, in 1785, proved that this increase in bulk is due to the 

 decomposition of ammonia into nitrogen and hydrogen, whilst Henry 

 and Davy ascertained that two volumes of ammonia are resolved into 

 one volume of nitrogen and three volumes of hydrogen. 



The early history of sal-ammoniac and of ammonia is very obscure. 

 The salt appears to have been brought into Europe from Asia in the 

 seventh century, probably from volcanic sources. An artificial mode 

 of producing the ammoniacal salts from decomposing animal matter 

 was soon discovered, and the early alchemists were well acquainted 

 with the carbonate under the name of spiritus satis urince. In later 

 times sal-ammoniac was obtained from Egypt, where it was prepared 

 by collecting the sublimate obtained by burning camels' dung. 



Although we are constantly surrounded by an atmosphere of 

 nitrogen, chemists have not yet succeeded in inducing this inert sub- 

 stance to combine readily, so that we are still dependant for our 

 supply of combined nitrogen, whether as nitric acid or ammonia, upon 

 the decomposition of the nitrogenous constituents of the bodies of 

 plants and animals. This may be effected either by natural decay, 



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