396 ZINC, CADMIUM, LEAD, c. 



will appear from the following experiment : 15 

 grains of pure galena or sulphuret of lead were 

 reduced to powder, and digested with nitric acid 

 in a small retort, the weight of which had been 

 previously ascertained, and marked upon it with 

 a diamond. By this process the galena was gra- 

 dually converted into sulphate of lead. When 

 the conversion was completed, the nitric acid 

 was distilled off, and the retort was kept in a 

 heat of above 600, till it became quite dry in 

 the inside ; it was then allowed to cool, and the 

 weight of the sulphate of lead thus formed was 

 exactly 19 grains. Now, 5 of these grains are 

 sulphuric acid, containing 2 grains of sulphur ; 

 consequently, 2 represents the quantity of sul- 

 phur in 15 grains of sulphuret of lead. The re- 

 mainder of the weight being lead, it is obvious 

 that sulphuret of lead is composed of 



Lead . . 13 



Sulphur . . 2 



15 



2 represents the weight of an atom of sulphur, 



and 13 is obviously the atomic weight of lead. 

 2. Besides the protoxide, or yellow oxide of 



lead, there are two other oxides of this metal ; 



namely, the red oxide, or deutoxide, and the 

 Com osi b rown oxide, or peroxide. 

 tionofred The beautiful pigment called red lead, is a 



