So Sir H. Davy on a new Substance 
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 inflammation as in muriatic acid gas, but the potas- 
sium becomes converted into a body, 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, 
neutralized by potash, and acted on by sulphuric acid, affords 
the peculiar substance. 
When the difficultly fusible substance it forms with phos- 
phorus is acted on by a small quantity of water, and heated 
in a glass tube, much gas spontaneously inflammable is dis- 
engaged, and a white sublimate arises, which, when 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, neu- 
tralized by potash, and decomposed by sulphuric acid, afforded 
the peculiar substance, but when the solution was heated 
strongly before its neutralization, it left only hydrophospho- 
rous acid, which when heated gave off hydrophosphoric gas, 
and became phosphoric acid. 
It is easy to explain all these phenomena, except the pro- 
duction of the acid gas, which is a compound of the peculiar 
substance and hydrogen : to account for the appearance of 
