CADMIUM. 67 



subacetates of lead, made by boiling a solution of the acetate in 

 litharge. 



Nitrate of kad, prepared by the action of nitric acid on lead. 

 Nitric acid is the proper solvent of lead ; — it is soluble. 



Sulphate of lead, prepared by the action of a soluble sulphate, on 

 a solution of the acetate of lead; it is a very insoluble salt. Cold 

 sulphuric acid has no action on lead ; but when boiling, the lead is 

 slowly oxidized at the expense of the acid. Hydrochloric acid has 

 no action on lead. 



Tests. — The alkaline carbonates throw down the insoluble carbo- 

 nate ; the soluble sulphates throw down the insoluble sulphate ; and 

 sulphuretted hydrogen or a soluble hydrosulphate, throws down the 

 black sulphuret. 



ZINC. 



Occurs in nature as a carbonate, {calamine), or as a sulphuret, 

 (zinc blende.) It is procured from the former by heat and charcoal ; 

 and from the latter by a similar process, after roasting the ore ; at 

 a high temperature, the metal, being volatile, comes over by dis- 

 tillation. 



Prop. — A bluish-white metal ; has a crystalline texture ; sp. gr. 7 ; 

 brittle at common temperatures ; malleable between 250° and 300° ; 

 very brittle at 400°; melts at 773°, and at a bright red heat it boils 

 and burns with a brilliant green light, generating the oxide. It is 

 called spelter in commerce, and is never quite pure ; is slightly tar- 

 nished by exposure to the air. Symb. (Zincum) Zn. — Eq. 33. 



Oxide of Zinc, ZnO ; — prepared by burning zinc in the air, or by 

 heating the carbonate. It is a white, insoluble powder, the basis of 

 the salts of zinc. 



Chloride of Zinc, ZnCl. ; — prepared by heating metallic zinc in 

 chlorine, or by dissolving zinc in hydrochloric acid, and drying. It 

 is a white substance, has the consistence of butter, and hence called 

 butter of zinc; very deliquescent, and soluble in water and alcohol. 



The important salts of zinc, are the sulphate and the carbonate. 



Sulphate of Zinc, white vitriol; — made by acting on zinc with 

 dilute sulphuric acid; the water is decomposed, its oxygen going to 

 the zinc, and the hydrogen escaping. It is a white, crystalline, 

 soluble salt. 



Carbonate of Zinc, — occurs native, and may be formed by double 

 decomposition between any soluble carbonate and the sulphate of 

 zinc. 



CADMIUM. 



This metal is usually found associated with zinc, in the reduction 

 of which from its ores, the cadmium, being more volatile, flies off. 

 Prop. — It resembles tin in colour; very malleable; very volatile; 



