62 WHITE LEAD. 



the sulphate of lead is converted into carbonate, which, 

 after washing, is completely dissolved by nitric acid. 



Sulphate of lead is dissolved to a great extent by a 

 mixture of tartrate of ammonia and free ammonia. 

 From this solution it may be completely precipitated 

 by sulphide of ammonium as black sulphide of lead, 

 or by chromate of potassa, in the form of yellow chro- 

 mate of lead. 



The sulphate of lead may be reduced to the metallic 

 state by fusion with four times its weight of cyanide 

 of potassium. 



38. WHITE LEAD. 



2(PbQ, OO 2 )-fPbO,HO 



frequently mixed with BaO, SO.,, CaO, SO 3; CaO, 

 CQ 2 , or PbO, S0 3 . 



Pure white lead is perfectly soluble in dilute nitric 

 acid. The oxide of lead may be determined by igni- 

 tion, after drying at 100. In order to estimate the 

 water, a specimen, whjch has been dried at 100, is 

 ignited in a tube to which a weighed chloride-of-calcium 

 tube is attached. The carbonic acid, which is expelled 

 at the same time, is determined by loss. White lead 

 sometimes contains a small quantity of basic acetate of 

 lead, indicated by the odor of acetone which is per- 

 ceived when the specimen is ignited. 



White lead adulterated with chalk is likewise dis- 

 solved, with exception of traces of impurities, by nitric 

 acid. From the diluted solution, the lead is precipi- 

 tated by sulphuretted hydrogen, the sulphide of lead 

 collected upon a weighed filter, washed, dried at 100, 

 and weighed. From the solution, after neutralizing 

 with ammonia, the lime is precipitated by oxalate of 

 ammonia. 



If barite be present in the specimen, it is left be- 



