of Atmospherical Air, Bc. 145 
calcination, or by means of the nitric and sulphuric 
acids (provided they are free from the acids) are es- 
sentially the “same. It must also be allowed by 
those who maintain that mercury contains phlogis- 
ton, that it has lost the whole of it in becoming the 
red oxyd, as it now shews no longer any properties 
attributed, to phlogiston, and is not capable of far- 
ther dephlogistication. 
But not only all the oxyds of mercury, but the 
oxyds of silver and gold also are reduced to their 
metallic state by mere heat. When silver is pre- 
cipitated from its solution in nitric acid, it is in the 
state of an oxyd of a dark brown colour, which 
weighs 12 per cent. more than the silver which was 
employed.* Gold, when precipitated from its solu- 
tion in nitro-muriatic acid, is an oxyd of a dark red 
colour, and weighs 10 per cent. more than the me- 
tal employed.t Both these oxyds are reduced to 
their metallic state by mere heat, without addition of 
any substance supposed to contain phlogiston; yet 
they must have lost their phlogiston, since nitrous 
air is produced during their solution in the acids, 
The hydrogenous gas, which is produced in dis- 
solving some metals in some of the acids, is attri- 
* Bergman, Dissertation on Metallic Precipitates, 
+ Ibid, 
VOL. V. T 
