ZINC. 
703 
§§ 898, 899.] 
§ 898. Chloride of Zinc is obtained by dissolving zinc in hydro¬ 
chloric acid, or by direct union of zinc and chlorine. Chloride of zinc 
is the only constituent in Burnett's disinfectant fluid,” which is seldom 
used now. A solution of chloride of zinc may be heated until it becomes 
water-free ; when this takes place it still remains fluid, and makes a 
convenient bath, for heat may be applied to it above 370° without 
it emitting fumes to inconvenience ; at a red heat it distils. A con¬ 
centrated solution of zinco-ammonic chloride (2H 4 NClZnCl 2 ) is used for 
the purpose of removing the film of oxide from various metals preparatory 
to soldering. 
§ 899. Zinc in the Arts.— The use of zinc as a metal in sheeting 
cisterns, articles for domestic use, alloys, etc., is well known ; oxide of 
zinc enters largely into the composition of india-rubber. Sulphide of 
zinc has been employed as a substitute for white lead, and may possibly 
supersede it. Zinc white is further employed as a pigment, and, mixed 
with albumen, is an agent in calico-printing ; it is also used in the 
decoloration of glass, in the polishing of optical glasses, in some kinds 
of surgical gauze, and in the manufacture of artificial meerschaum pipes. 1 
Chromate of Zinc (ZnCr0 4 ) is used in calico-printing, and there is 
also in commerce a basic chromate known as zinc yelloiv. Zinc green, 
or Rinman’s green, is a beautiful innocuous colour, forming by igniting 
a mixture of dry zincic and cobaltous carbonates. 
The use of zinc vessels in the preparation of foods may occasionally 
bring the metal under the notice of the analyst. When exposed to 
a moist atmosphere, zinc becomes covered with a thin film of oxide, 
perfectly insoluble in ordinary water ; but, if the water should be 
charged with common salt, a considerable quantity may be dissolved. 
It may generally be laid down as a rule that the solvent power of water 
on zinc has a direct relation to the chlorides present, whilst carbonate of 
lime greatly diminishes this solubility. 2 
Milk may become contaminated by zinc; for it is a matter of com¬ 
mon knowledge that milk contained in zinc vessels does not readily 
turn sour. This may be explained by the zinc oxide combining with 
the lactic acid, and forming the sparingly soluble lactate of zinc 
2(C 3 H 5 0 3 )Zn + 3H 2 0, thus withdrawing the lactic acid as fast as it is 
formed, preventing the coagulation of the casein. With regard to this 
important practical subject, MM. Payne and Chevallier made several 
experiments on the action of brandy, wine, vinegar, olive oil, soup, 
milk, etc., and proved that zinc is acted on by all these, and especially 
by alcoholic, acetic, and saline liquids. M. Schauflele has repeated these 
1 Artificial meerschaum pipes are composed of zinc white, magnesia usta, and 
casein ammonium. 
2 Ziurek, indeed, found in a litre of water contained in a zinc cistern no less than 
1-0104 grm. of zinc, and the same water showed only 0-074 grm. of common salt to 
the litre.— Vierteljahrsschr. f ur gericht. Medicin, vi. 356, 1867. 
