USEFUL JI//.T.1/.N 125 



most effective point. The spent tan resulting therefrom i- 

 of superior quality and its concent nil re I extract is sold to the 

 leather tanneries. 



Litharge is another important lead pigment. Its most impor- 

 tant use is that of a pigment. It is used also as an ingredient in 

 the compounding of rubber, in 1 he manufact ure of glass, in assay- 

 ing, mixed with glycerine to hold pipes and table tops together. 

 It may be manufactured from several lead salts by roasting them 

 to drive off the volatile acid radicle. The powder obtained is a 

 buff yellow, but if heated to the point of fusion reddish-yellow 

 scales of the oxide appear. This product is known in the marts 

 of trade as litharge. It is obtained in large quantities during the 

 desilverization of lead. 



Another lead pigment of considerable importance is red lead. 

 It is not only used as a pigment but also in the manufacture of 

 flint glass, and very extensively in the production of structural 

 steel. It is also used as a pipe-joint cement. It can be manu- 

 factured by heating for a considerable time various salts of lead 

 at a temperature of 450. 



Orange mineral is another lead pigment of less commercial 

 significance. It can be manufactured by the treatment of 

 soluble salts of lead with sodium oxychloride in the presence of an 

 alkaline hydrate. 



Sublimed blue lead is obtained as a by-product in the sublima- 

 tion of galenite and consists of a mixture of lead oxide, lead 

 sulphide, lead sulphite, zinc oxide and carbon. It is used in the 

 manufacture of rubber goods. 



Lead arsenate is used also in the destruction of the gypsy moth. 



The production of lead includes base bullion, pig lead, bars, 

 sheets and old lead. Pig lead is reported by all smelters operating 

 in the Mississippi Valley. Refined lead embraces all of the de- 

 silverized lead produced in this country, and the pig lead recov- 

 ered from the Mississippi Valley lead industry. Antimonial lead 

 is derived from the treatment of gold and silver ores bearing 

 antimony. In the process of extraction of the precious metals 

 the antimony combines with the lead in the formation of anti- 

 monial lead. For this product there is quite a large demand 

 and the two metals are never separated. 



In 1885 there began in the United States the treatment of for- 

 eign ores and base bullion largely from Mexico. Part of this prod- 

 uct is smelted and exported, but a considerable quantity is con- 



