USEFUL METALS 267 



Zinc is used in the manufacture of zinc oxide, or zinc white, 

 which is now extensively used as a pigment in the place of white 

 lea<l. It is manufactured ly burning metallic zinc in an atmos- 

 phere of oxygen or in a current of air. It does not equal white 

 lead in covering power or body, but it is vastly superior to white 

 lead wherever the walls of the building are exposed to the action 

 of hydrogen sulphide, as in chemical or mineralogical labora- 

 tories, and in cities and towns where large quantities of coal are 

 consumed. 



Zinc is used also in the manufacture of zinc salts for the 

 chemical trade. Perhaps the most important salt of zinc is the 

 chloride. It is used to a limited extent in dentistry for spongy 

 gums. It is utilized extensively in preserving railroad ties. 

 The tie is immersed in a solution of zinc chloride, and after 

 becoming thoroughly saturated, the life of the tie is much 

 prolonged. This new use is increasing rapidly with many of 

 the larger railroads. 



Zinc is used also, in electrolysis and in the manufacture of 

 white vitriol. It is used in the manufacture of lithopone, a 

 pigment consisting of barite, zinc oxide, and zinc sulphate. 

 The industry is carried on to a considerable extent by the New 

 Jersey Zinc Company and by the Grasselli Chemical Company. 

 White vitriol is largely consumed in the manufacture of glue and 

 special paints. 



The most important commercial and technical change in the 

 zinc industry in recent years appears in the predominance which 

 the natural gas smelters of Kansas have gained over those depend- 

 ing upon coal for a fuel. The Joplin ores were formally treated 

 at LaSalle and Peru, Illinois, St. Louis, Missouri, and Pittsburg, 

 Kansas. The first two were smelting centers long before the 

 history of zinc began at Joplin. The last is only 26 miles from 

 Joplin and owes its development to the local coal production. 

 The use of natural gas has resulted in closing down the coal 

 smelters and the installation of gas smelters. 



