ON THE OXIDES OF LEAD. 281 



fcoured fo iuccefsFully in this department as Mr. Prouft. ToAnalyfesof 

 him we are indebted for the anal)'fis of the oxides of zinc,' '^°'^ ' 

 iron, tin, copper, anUmouy, and arfenic. His diderlalions 

 are all ftamped witli the charadler of originality, and difplay 

 fo much Ikili and candour, that they never fail to command 

 the confidence of the reader. If he fom^times pufties his con- 

 fequences a little too far, he more than corapenfates for this 

 by the originality of his views, and the new light which he 

 throws upon every fubjeft that he difcufTes. 



I intend at prefent to offer fome obfervations on (he oxides ^"^j^'? of this 

 of lead, a fubject more than once flightly touched upon by oj^jtjgj (,f je^j^ 

 Prouft, but never fully difculTed by him. I truft the difficulty 

 of the fubje6t will plead my excufe, if I fliall be unfortunate 

 enough to fall into miflakes. 



We are acquainted with three oxides of lead fufficientiv '^'^'■" ^''^'""^ 

 diftinft from each other. The firft is of a yellow colour, and "g^ ^brown "and 

 forms the bafe of almott all the falts of lead; the fecond is a two others. 

 paint well known by the name of red lead; the third a brown 

 powder difrovered by Scheeie, and examined more lately by 

 Prouft and Vauquelin. Befides thefe three, a fourth has been 

 announced by Prouft ; and litharge has been confidered jjy 

 fome as conftiluting a fiflh. Let us examine thefe oxides. 



I. Yellow Oxide. 



The yellow pigment called mafficot confifts eftentlally of this Yellow oxide of 

 oxide; but the eafieft method of forming it, is to diflolve lead 

 in nitric acid. Pure lead diffolves completely in that acid ; 

 but the lead of commerce ufually leaves a fmall quantity of 

 grey powder, which confifts for the moft part of oxide of 

 antimony, foinelimes mixed with a little fi'ica. Whc-n the 

 folution is concentrated by evaporation, we obtain cryfta's of 

 nitrate of lead, a fait too well known to require any particular 

 defcription. 



1. When the cryftals of nitrate of lead thus obtained by Nitrate of lead, 

 1 11 1 • 1 1 1 .!• r I lofes acid by low- 



evaporation, and well dried upon blotting-paper, are expojed j^^^^j. ' 



to a temperature of about 300*, they lole, at an average, 



three per cent, of their weight. This lofs is not to be afcribed 



to the efcape of mere water, for the fumes fmeji ftrongly of 



pitric acid. 



* 2. When 69 grains of lead are diftblved in nitric acid, and — 'e^'^ tont/in. 



the folution evaporated to drynefs, the nitrate of lead, after ^ 



'- being 



