THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[THIRD SERIES.] 



SEPTEMBER 1844. 



XXIV. On Coal- Gas. By Thomas Thomson, M.Z)., 

 F.R.S. L, andE., M.R.I. A., Regius Professor of Chemistry 

 in the University of Glasgow*. 



IT is well known that the word gas was first introduced into 

 chemistry by Van Helmont in his Treatise de Flatihus. 

 Junker, whose Conspectxis Chemice Theoretico Practice was 

 published in 1744, conjectures that Van Helmont's word gas 

 was merely the German word gcischt, fermentation, in a Latin 

 dress, and this conjecture seems as probable as any. 



Boyle was the first chemist who attempted to make gas ar- 

 tificially, and who showed that thus prepared it possessed the 

 mechanical properties of common air. The gas which he ex- 

 amined was hydrogen, obtained by pouring dilute sulphuric 

 acid on iron filings. 



Hales, in 1726, proved by experiment that many animal 

 and vegetable substances, when heated sufficiently, give out an 

 air which possesses the mechanical properties of common air, 

 and which therefore he considered as not differing in its pro- 

 perties from common air. That hydrogen gas was combustible 

 was known at least as early as the beginning of the last century, 

 and many remarkable stories are told by early chemists of the 

 eighteenth century, about its combustibility, and the violent 

 explosions which a mixture of it and common air produced 

 when brought in contact with a burning body. 



Dr. Black first showed that carbonic acid, though a gas, 

 differed essentially from common air, and he gave it the name 

 oifxed air, because it existed in a solid state in the carbonates. 

 Cavendish, in 1766, showed that hydrogen differs from com- 

 mon air and from carbonic acid ; he examined its combusti- 

 bility, its specific gravity, and pointed out its peculiarities. In 

 1772 Dr. Priestley began his experiments on air ; first he exa- 



* Read before the Philosophical Society of Glasgow, November 1, 1843; 

 and communicated to this Journal by the author. 



Phil. Mag. S. 3. Vol. 25. No. 165. Sept. 1844. M 



