tvklch hecomes a violet-coloured Gas ly Heat. 7 



"billing with the aqueous vapour in tlie air. It has a smell very 

 similar to that of the solid compound of chlorine and phos- 

 phorus, which itself is very analogous to that of muriatic acid. 

 It is rajiidly absorbed by water. When made to act upon am- 

 monia, it forms with it a dense white salt, which, when acted 

 upon by sulphuric acid, affords the peculiar substance, and at the 

 same time a smell of hydrogen is perceived. When mercury is 

 heated in the acid gas, the same compound as that produced by 

 the action of the new substance directly upon mercury is formed, 

 and hydrogen equal to half the volume of the gas is disengaged. 

 When potassium is made to act upon it, there is no inflamma- 

 tion as in muriatic acid gas, but the potassium becomes con- 

 verted into a Ijody similar to that produced by its combustion in 

 the vapour of the substance, and a gas equal to half the volume 

 of the acid gas, which burns in the same manner as hydrogen, 

 is disengaged. 



When the easily fusible and volatile compound of the sub- 

 stance with phosphorus is heated in water, it rapidly dissolves 

 in it, and forms a strong acid, which, when evaporated, leaves 

 hydrophosphorous acid, and which, before its evaporation, ' neu- 

 tralized by potash, and acted on by sulphuric acid, afi'ords the 

 peculiar substance. 



When the difficultly fusible substance it forms with phnspho- 

 nis is acted on by a small quantity of water, and heated in a 

 glass tube, much gas spontaneously inflammable is disengaged, 

 and a white sublimate arises, which, wlien acted on by cold 

 water, becomes hot, and affords a considerable quantity of a gas 

 having all the properties of hydrophosphoric gas. 



The solution of this crystalline substance in water, neutra- 

 lized by potash, and decomposed by sulphuric acid, afforded the 

 peculiar substance ; but when the solution was heated strongly 

 before its neutralization, it left only hydrophosphorous acid, 

 which «'heu heated gave oft' hydrophosphoric gas, and became 

 phosphoric acid. 



It is easy to explain all these phaenomena, except the produc- 

 tion of the acid gas, Vv'hich is a compound of the peculiar sub- 

 stance and hydrogen: to account for the appearance of this 

 body, it is necessary to suppose the existence of hydrogen or 

 of water in the substance, or of hydrogen in ))hosphorus. 



I used the substance distilled through quick lime, which there 

 is every reason to believe would absorb all the water ui\ited to it: 

 in this case the acid gas, which gave hydrogen when decom- 

 posed by mercury, was produced in much smaller (juantities ; 

 but, when the substarwee was moistened, the gas was afforded in 

 very large quantities It is probable, that a little hydrogen 



A 4 existing 



