COPPER, ZINC, LEAD, ETC. 151 



oxid, Pb 2 O, is produced when lead is exposed to the air; 

 in a pure condition, it is a black powder. Lead oxid, 

 PbO, is a yellow powder which, if heated, produces 

 litharge, a yellowish red material. This substance is ob- 

 tained largely in the separation of lead from silver. Lead 

 peroxid, PbO 2 , is an oxidizing agent, and in some respects 

 resembles manganese dioxid. Red led or minium, Pb 3 O 4 , 

 is produced by heating lead oxid, and is used as a pig- 

 ment. 



198. Lead Carbonates. The normal carbonate, PbCO 3 , 

 is occasionally found in nature. The basic carbonate, 

 Pb(OH) 3 .3PbCO 3 , is common white lead, which is exten- 

 sively used as a pigment. It is produced by different 

 methods from litharge and other compounds of lead, as 

 well as by treatment of the metal itself. 



199. Lead Salts. Lead nitrate, Pb(NO 3 ) 2 , is produced 

 by the action of nitric acid on lead ; and lead sulfate, by 

 the action of a sulfate upon a soluble lead salt. Lead 

 chlorid, PbCl 2 , is precipitated whenever a chlorid or hy- 

 drochloric acid is added to a solution containing a lead 

 salt. The salts of lead are more insoluble than those of 

 many other metals. 



200. Uses of Lead. Lead is used for making water 

 pipes, for lining tanks, particularly those in which sul- 

 furic acid is stored, in the preparation of solder, and in 

 many alloys. Lead is insoluble in most waters although 

 the salts and organic matter in some waters may cause a 

 sufficient amount to dissolve to render the use of lead 

 pipes objectionable from a sanitary point of view. 



