102 ELECTROLYSIS. 



varied as interesting, either in the nature of a coating on other 

 metals, or in a state of purity, or in various alloys. 



PHYSICAL PROPERTIES. In a state of purity, the metal 

 nickel is hard, ductile, not easily fusible, and capable of receiving 

 a beautiful polish. Its colour lies between whitish silver and 

 greyish steel. Its density varies between 8 '3 and 9 '2; it is 

 equal to 8 '34 when cast, to 8 -50 when reduced by hydrogen, 

 and to 8 80 when in a forged state. 



Its tenacity is, compared to that of iron, as 9 : 7. It can be 

 easily forged, rolled, or drawn. 



Nickel is magnetic at the ordinary temperature. Its mag- 

 netic property disappears at a temperature of 350 Cent. 

 Under the influence of low magnetising forces, its magnetism 

 is five times stronger than that of iron ; with considerable 

 magnetising forces it is five times less. 



CHEMICAL PROPERTIES. Nickel is soluble only in sulphuric, 

 nitric, and hydrochloric acids. It combines directly with 

 chlorine, phosphorus, sulphur, and arsenic. 



Nickel is dissolved by dilute nitric acid ; in concentrated 

 nitric acid it is rendered passive. 



Cold or hot air has no action on nickel, but certain alimen- 

 tary substances, such as hot lard, rapidly dissolve it ; beer, 

 mustard, tea, and other infusions considerably alter its colour ; 

 the nickeling of cooking or culinary utensils, such as saucepans, 

 spoons, forks, &c., is therefore not to be recommended. 



59 

 The chemical equivalent of nickel is -^ = 29 5. 



Jj 



HEAT DUE TO THE FORMATION OF DOUBLE SALTS. The 

 double sulphate of nickel and ammonium developes 94*8 

 calories per equivalent, starting from the metal NH 3 -)- H and 

 from the radical S0 4 . 



The double chloride of nickel and ammonium developes 

 98 '65 colories per equivalent from the metal NH 3 + H and 

 the chlorine. 



NICKELING. In the following study we will take for our 

 guides : M. Perille, one of the best nickel-platers of Paris, who 

 kinHly put both his factory and his formulae at our disposal ; 

 M. Pfanhauser, of Vienna, who has published on the subject 



