1814.] Constituents of Azote. 189 



it, and to be always disengaged from it whenever it enters into 

 combination ; and a residuum of azotic gas. Its action on the 

 various re-agents must be attributed entirely to the agency of the 

 peculiar portion, and the chemical effects of this mixture will 

 therefore be enumerated as the properties of the acid gas. It will 

 afterwards be my object to develope from these experiments the 

 nature of the changes that have taken place throughout the 

 whole series of operations. 1 shall designate the air extracted from 

 the flask for examination by the name of the mixed gas ; and the 

 portion to which it owes its peculiar properties, the acid gas. 



Properties of the Acid Gas. 



The specific gravity of the mixed gas is 01)3'18, 100 cubic 

 inches weigh 28*5 grains; but it will afterwards be shown that the 

 specific gravity of the acid gas is L • 1 fcr, and that 100 cubic inches 

 weigh 35-38 grains. Whether it has the smell of the mixed gas, 

 or whether that odour is owing to its combination with hydrogen 

 (as is the case with sulphureted hydrogen), I am not able to deter- 

 mine. The hydrogenated acid gas is inflammable, burning with a 

 blue lambent flame, and explodes when previously mixed with a 

 certain portion of atmospheric air. The acid gas is colourless and 

 permanently gaseous over mercury, but it tarnishes rapidly the 

 surface of the metal ; arid when kept over it a long time, the gas 

 diminishes slowly in volume, a black substance floating on the sur- 

 face, and adhering to the lube, which is a combination of the mer- 

 cury with the acid gas. 



It is absorbed by water most rapidly; on passing the mixed gas 

 through a column of water once or twice, nearly the whole of the 

 absorbable portion is condensed, the. amount of the entire diminu- 

 tion being 3y per cent. Although this quantity only would appear 

 to be absorbed by water, yet it will afterwards be shown that in 

 reality about .SO per cent, are dissolved ; the hydrogen which existed 

 in a condensed state in combination with the acid gas is liberated, 

 and hence assumes a larger volume than it occupied when in a 

 state of combination : the actual absorption is therefore in appear- 

 ance diminished by the excess of volume which the hydrogen 

 occupies in its natural state over that it possesses when in the 

 condensed state of combination with the acid gas. The acid gas is 

 itself wholly soluble in water, which takes up twice its volume. 

 The aqueous solution has the property of precipitating metals from 

 their solutions in the same state as is produced by the acid gas. It 

 has the peculiar smell of the gas, and lias a fetid saline taste. 



0*22 cubic inches of the mixed uas were | ass ' up into Volta's 

 eudiometer over mercury, through which several electrical discharges 

 were scut without any effect : <> 25 cubical inches of atmospheric air 

 were then added to it ; but still the ^hoek produced no ctlect. 

 Twelve hour* afterwards I observed a pretty copious deposition of a 

 yellow substance (mosi probably a portion of its sulphur) on the 

 iiiiide of the tube, but the \oIume of the gases remained un- 



