68 MATERIA MEDIC A AND THERAPEUTICS. 



Characters. Colourless prisms, with a metallic 

 styptic taste. 



Impurities. Iron, lead, copper, arsenic. 



Dose. 1 to 3 gr. as a tonic ; 10 to 30 gr. as an emetic. 



From Zinci Sulphas are made : 



a. Zinci Carbonas. Carbonate of Zinc. 

 ZnC0 3 (ZnO) 2 3H 2 O. "Calamine.' ' 



Source. Made by decomposing a solution of 

 Sulphate of Zinc with a solution of Carbonate of 

 Soda. (1) ZnSO 4 + Na 2 C0 3 = ZnC0 3 -f Na 2 S0 4 . 

 (2) 3ZnC0 3 + 3H 2 = ZnC0 3 2(ZnO),3H 2 + 2C0 2 . 



Characters. A white, tasteless, inodorous 

 powder, insoluble in water ; an impure carbonate. 



Impurities. Sulphates, chlorides, copper. 



From Zinci Carbonas are made : 



(i) Zinci Qxidum. Oxide of Zinc. ZnO. 



Source. Made by heating the Carbonate. 



Characters. A soft, nearly white, tasteless, 

 and inodorous powder, insoluble in water. 



Impurities. The carbonate; effervescing 

 with acids. And its impurities. 



Dose. 2 to 10 gr. 



Preparation. 



TJnguentum Zinci Oxidi, 80 gr. to 

 1 oz. Benzoated Lard. 



fii) Zinci Acetas. Acetate of Zinc. 

 Zn(C 2 H 3 2 ) 2 .2H 2 O. 



Source. Made by dissolving Carbonate of 

 Zinc in Acetic Acid and Water, and crystal- 

 lising. ZnC0 3 ,2Zn0.3H 2 + 6C 2 H 4 2 = 

 3(Zn2C 2 H 3 O 2 ) + 6H 2 + C0 2 . 



Characters. Thin colourless crystalline 

 plates, of a pearly lustre, with sharp, unpleasant 

 taste. Solubility, 10 in 25 of water. 



Impurities. Those of the carbonate. 



Dose. 1 to 2 gr. as tonic ; 10 to 20 gr. as 

 an emetic. 



Zinci Carbonas is also used in making Zinci 

 Chloridum and Zinci Sulphas. 



B. Zinci Valerianas, Valerianate of Zinc. 



Zn(C 5 H 9 O 2 ) 2 . 



Source. Made by mixing solutions of Sulphate 

 of Zinc and Valerianate of Soda, and crystallising. 



