In the Red Lead of Sller'ta, 363 



Tn tliis operation the muriatic acid, as is evident, com- 

 bines with it in virtue of a greater affinity to the lead, from 

 which it Separates the natural acid, which is then diflblved in 

 the water of the muriatic acid. When fuitable proportions 

 of the acid, water, and lead have been-employed, if the liquor 

 be evaporated by a gentle heat and without the contact of 

 light, you may obtain cryitals of the acid of a ruby red 

 colour. But if too great a quantity of the acid be effect, 

 or an acid too much concentrated ; and, above all, if heat 

 has been employed in the procefs ; inftead of a red acid . 

 you will obtain a dark green liquor, which is then a com- 

 bination of the oxyde of the new metal with the muri- 

 atic acid. It will be feen hereafter what are the caufes of 

 ihefe effential differences : at prefent it is fufficient to men*- 

 tion them. 



The fulphuric acid decompofes alfo the red lead, by laying 

 hold of the oxyde ; but I did not employ it to extract the 

 acid, becaufe, if ever fo little a quantity more than is necef- 

 fary he added, it is very difficult to feparate it. 



The nitric acid does not produce any change in the nature 

 of the red lead, only that when aided by the action of heat 

 it effects its folution ; but on cooling, the greater part of the 

 red lead feparates itfelf with all its properties. 



Exp. II. ABion of Alkalies on the Red Lead. 



Cauftic alkalies do not feem to decompofe the red lead, 

 for they diffolve it entirely, and form with it a kind of triple 

 combination; the properties of which I did not examine 

 minutely. 



Alkaline carbonats, on the contrary, decompofe the red 

 lead completely; and there is formed, on the one hand, 

 carbonat of lead ; and on the other, a foluble fait compofed 

 of the metallic acid and of the bafe of the carbonat em- 

 ployed. 



The falts formed by this acid with alkalies cryftallife into 

 prifms, or into laminae of a golden yellow colour, the forms 



of 



