and the Arsemate of Nickel of Allemont. 299 



with charcoal, as in iron assays, gave a well-melted button of 

 arseniuret of nickel weighing 6* 15 gr. It was grey without any 

 tint of red, brittle, the fracture granulated, almost even, and 

 somewhat approaching to lamellar ; in its centre it contained a 

 cavity lined with brilliant needles ; it was not at all magnetic. 

 This compound contained nearly a half part less of arsenic than 

 the native arseniuret of nickel, and consequently one atom of 

 arsenic to two of nickel. 



The Sulphate of Nickel crystallizes in long oblique prisms with 

 rhomboid bases, and changes into hexaedral prisms by a facet on 

 each obtuse angle. These crystals are perfectly transparent, and of 

 a beautiful emerald green. By exposure to'air and solar light they 

 gradually effloresce, and become opake without losing their form. 

 When calcined, this sulphate was composed of 0*478 per cent, 

 of protoxide of nickel, and 0o22 of sulphuric acid. Ten grains 

 of this sulphate reduced in a charcoal crucible at the heat of an 

 iron assay, gave a well-melted button of sulphuret, which was 

 grey with a shade of yellow, brittle, with a fracture lamellar in 

 one direction, and granulafed in the other, and strongly mag- 

 netical. It appears to consist of 1 atom of sulphur and 2 of 

 nickel. 



The Carbonate of Nickel obtained by precipitating a solution 

 of this metal with a subcarbonated alkali, is of a fine apple-green 

 verging to yellow, and retains this colour after exposure to the 

 sun. If it contains ever so little cobalt its tint is sensibly altered, 

 and passes to a dirty greyish violet. 

 It is composed oi 



Protoxide of nickel 0-475 



Carbonic acid , 0' 1 40 



Water 0-385 —1000 



This salt appears to contain 1 atom of acid to 1 atom of oxide. 



When a saturated carbonate instead of a subcarbonate is 

 employed, the precipitate is of a very pale green, and becomes 

 light and pulverulent when dried in the sun. 

 It consists of 



Protoxide of nickel 0-483 



Carbonic acid 0-210 



Water 0-307 I'OOO 



It appears to contain 3 atoms of acid to 2 of base. 



These carbonates of nickel are readily decomposed by heat. 

 When they are calcined in a dull red heat with exposure to air, 

 they produce a fine black peroxide of nickel, but in a stronger heat 

 this changes to a pure olive-coloured protoxide. 



XLVI. No- 



