364 On the Metal contained 



of which I have not been able to determine accurately, c* 



account of the fmall quantity I could make. 



Thefe falts have a flight metallic tafte : they diilblve with 

 effervefcence, and afl'ume a green colour : they are decom- 

 pofed by acids and alkaline earths, which form orange yellow 

 precipitates. 



Exp. III. Atlion of Acids on the Acid of the Red Lead. 



Among the mineral acids, the muriatic is the onlv our 

 which acts in a remarkable manner on that of the red lead. 

 Indeed, whether the red lead be diftillcd, or its acid with the 

 muriatic acid a little concentrated, there is foon difengaged 

 oxygenated muriatic acid, and the liquor affumes a very 

 beautiful green colour. The caufe of this may be readily 

 conceived : the muriatic acid takes from that of the load a 

 part of its oxygen, ar.d reduces it to the ftate of a green 

 oxyde, which is held in folution by another portion of the 

 muriatic acid. 



As this experiment announced to me that the oxygen does 

 not adhere ftrongly to that metal, I was defirous to know 

 whether its acid mixed with the muriatic acid would diflblve 

 gold : I therefore put into this mixture a piece of gold leaf, 

 which was dilfolved in a little time by the help of a gentle 

 heat, and the folution had a yellowifh -green colour. This 

 acid then produces the fame effect as the nitric acid in aqua*- 

 regia, in regard to the folution of gold. 



The fulphuric acid, cold, produces no effccT: upon this acid; 

 but when warmed it makes it aillune a blueifh green colour, 

 by favouring, no doubt, the difengagement of a portion of 

 its oxygen, as it does in regard to the oxyde of manganefe 

 and the acids of tungften and molvbdena. 



The fulphurous acid lays hold of a prut of the oxvgen of 

 this acid, becomes fulphuric acid, and reduces that of th« 

 lead to the ftate of an oxyde, which it difiblves. 



Exp, 



