420 COMPOUNDS OF CARBON. 



are, therefore, not isomorphous with sal ammoniac. They are 

 decomposed by water, with evolution of phosphuretted hy- 

 drogen. 



Phosphuretted hydrogen, like ammonia, combines with the 

 perchlorides of tin, titanium, chromium, iron, and antimony, 

 forming white saline bodies. The combination with bichloride 

 of tin is decomposed, with escape of the gas in the non-in- 

 flammable state, by water, and in the self-inflammable condition 

 by solution of ammonia. 



CHAPTER III. 



COMPOUNDS OF CARBON. 



SECTION I. 

 CARBON AND HYDROGEN. 



Light carburetted hydrogen, C H 2 . This gas is a constant 

 product of the putrefactive decomposition of wood and other 

 compounds of carbon, under water, and is most readily obtained 

 by stirring the mud at the bottom of stagnant pools, and col - 

 lecting the gas as it rises in an inverted bottle and funnel. It 

 always contains 10 or 20 per cent of carbonic acid, which may 

 be separated from it by lime-water, and a small proportion of 

 nitrogen. Carburetted hydrogen also issues, in some places, in 

 considerable quantities from fissures in the earth, coming often 

 from subterraneous deposits of coal ; and in the working of coal 

 mines, it is found pent up in cavities, and would appear some- 

 times to be discharged from the fresh surface of the coal in 

 sensible quantity. Hence, this gas is sometimes described as 

 the inflammable air of marshes, and the fire-damp of mines. 

 It is the most considerable constituent of coal gas, and of the 

 gaseous mixture obtained on passing the vapour of alcohol 

 through an ignited porcelain tube, but no artificial process is 

 known to afford this gas in a state of purity. 



The density of light carburetted hydrogen is 559.5, and 1 

 volume of it contains 1 vol. of carbon vapour, and 2 vols. of 



