ON THE OXIDES OF LEAD, 29 1 



Litharge confifts of fcales, partly of a golden yellow colour Litharge j 

 and partly red : They poflefs a certain degree of elaflicity. 

 Tlie method of making litharge has been defcribed by Dr. 

 Watfon, by Gmelin, and by other chemical writers. 



1. When 100 grains of litharge are expofed to a red heat, contains carbo* 

 they melt into a yellow glaze, and lofe, at an average, four"^^^* 

 grains of their weight. When 50 grains of pounded litharge 



are thrown into nitric acid, they diffolve with efFervefcence, 

 and lofe two grains of their weight. The efFervefcence and 

 Jofs of weight are owing to the efcape of carbonic acid gas. 

 From this we may conclude^ that litharge contains four per 

 cent, of carbonic acid* 



2. When 50 grains of litharge were diffolved in nitric acid, and antimony; 

 and the Iblution evaporated to drynefs and re-ditTolved in 



water, l|- grains of a grey powder remained behind in my 

 trials, which proved to be oxide of antimony. Therefore, 

 litharge contains three per cent, of oxide of antimony. 



3. The foluUon evaporated to drynefs, gave 68. 5 grains ofComp. parts in- 

 nitrate of lead; but this nitrate contains 46.72 grains of yellow ^^^^^"^^*^ ' 

 oxide of lead, Ofcourfe, we have litharge corapofed of 



93.44 yellow oxide of lead, 

 3.00 oxide of antimony, 

 4.00 carbonic acid. 



100.44 

 The final! excefs muft be afcrlbed to unavoidable errors in the 

 analyfis. 



4. Fifty grains of litharge diffolved in nitric acid, deprived 

 of its oxide of antimony, and then thrown down by carbonate 

 of potafli, gave 52\ grains of carbonate of lead. Hence 97 

 grains of litharge (fuppofing the antim.ony a foreign body) 

 would have given 105 grains of carbonate. But 97 grains of 

 litharge contain nearly four of carbonic acid. Hence we have 

 the carbonate formed of 93 oxide and 12 acid. 



In this experiment the carbonate produced was too fmall by 

 about a grain. This was partly owing to the lofs of a fmall 

 quantity of the powder while feparating it from the fiilre. As 

 I could not ellimate the lofs, I left it out in the calculation, 

 and dated the amount precifely as I found it» 



From the preceding experiments it follows, that litharge is a h is a fubcarboii 

 fub-carbonate of lead, lince it confifts effentially of about 96n»tc! 

 U 2 yellow 



