182 METALS AND THEIR COMBINATIONS. 



Zinc bromide, Zinci bromidum, ZnBr 2 = 224.7. Obtained 

 analogously to the chloride by dissolving zinc in hydrobromic acid ; 

 it is a white powder, resembling the chloride in its properties. 



Zinc iodide, Zinci iodidum, ZnI 2 = 318.1. The two elements 

 zinc and iodine combine readily when heated with water ; the color- 

 less solution when evaporated to dryness yields a powder whose 

 physical properties resemble those of the chloride. 



Zinc carbonate, Zinci carbonas prsecipitatus, 2(ZnCO 3 ).3[Zn 

 (OH 2 )] = 547.5 (Precipitated carbonate of zinc). Solutions of equal 

 quantities of zinc sulphate and sodium carbonate are mixed and 

 boiled, when a white precipitate is formed, which is a mixture of the 

 carbonate and hydroxide of zinc, corresponding more or less to the 

 formula given above. 



5ZnSO 4 + 5Na 2 CO 3 + 3H 2 O = 3CO 2 + 5Na 2 SO 4 + 2(ZnCO 3 ).3[Zn(OH) 2 ]. 



Precipitated zinc carbonate is a white, impalpable powder, odorless 

 and tasteless, insoluble in water, soluble in acids and in ammonia 

 water. 



Zinc sulphate, Zinci sulphas, ZnSO 4 .7H 2 O 287.1 ( White vit- 

 riol), is obtained by dissolving zinc in dilute sulphuric acid : 

 H 2 S0 4 + zH 2 + Zn = ZnSO 4 + zH 2 O + 2H. 



If zinc be added to strong sulphuric acid, no decomposition takes 

 place : no sufficient explanation has as yet been given for this fact. 



Zinc sulphate forms small, colorless crystals, which are isomorphous 

 with magnesium sulphate ; it is easily soluble in water. 



Experiment 30. Use the liquid obtained when performing Experiment 2, or, 

 if not left, dissolve a few grammes of metallic zinc in dilute sulphuric acid, 

 filter the solution, evaporate sufficiently, and set aside for crystallization. Use 

 the zinc sulphate thus obtained for the analytical reactions. State the quantity 

 of dilute sulphuric acid required for dissolving 5 grammes of zinc, and the 

 quantity of crystallized zinc sulphate which may be obtained. 



Zinc phosphide, Zinci phosphidum, Zn 3 P 2 = 257.3. The two 

 elements zinc and phosphorus combine readily when the latter is 

 thrown upon melted zinc, forming a grayish-black powder, or 

 minutely crystalline, friable fragments, having a metallic lustre on 

 the fractured surface. 



Antidotes. Soluble zinc salts (sulphate, chloride) have a poisonous effect. 

 If the poison have not produced vomiting, this should be induced. Milk, 



