238 CHEMISTRY. 



. 333. Chloride of Zinc, ZnCI 2 . This is a white substance 

 which is quite soft, and melts, if heated, a little above the 

 boiling point of water. "When the old names in chemistry 

 were in vogue, this substance, on account of its softness 

 and fusibility, had the name of butter of zinc. It has a 

 great attraction for water, and therefore is active as a caus- 

 tic, a use to which it is appropriated. While it thus de- 

 stroys when concentrated, if diluted it acts as a preserva- 

 tive against putrefaction, and is employed by the anatomist 

 for preserving bodies for dissection. 



Sulphate of zinc ZnSO 4 sometimes called white vitriol, 

 is a powerful emetic. It crystallizes in long, white needles, 

 and is very soluble in water. It is often obtained in the 

 laboratory as a residue in making hydrogen gas. Zinc, 

 sulphuric acid, and water yielding zinc sulphate and hy- 

 drogen, thus : 



Zn + H 2 S0 4 = ZnS0 4 + H a 

 334. Uses of Zinc. Though zinc is quite an abundant 

 metal, it was formerly used but for little else than making 

 brass and pinchbeck. The variety of uses to which it is 

 now applied comes from a discovery which was made in 

 regard to its malleability. When cold it is very brittle; 

 but when heated to within a certain range of temperature 

 (100 to 150 C.), it becomes quite malleable, and may be 

 rolled into thin sheets. It retains the malleability thus 

 acquired after it becomes cold. It is a curious fact that if 

 this metal be carried beyond the range of temperature al- 

 luded to, it becomes brittle again. When in this range it 

 becomes ductile as well as malleable. The discovery of 

 these facts has introduced this metal to very numerous 

 valuable uses. It is now used in the manufacture of many 

 articles which were formerly made of lead, copper, and iron 

 as nails, gasometers, gas-pipes, gutters, roofing, lining for 

 refrigerators and sinks, etc. It is harder and yet lighter 



