HISTORY OF COBALT AND NieKEL. 4f 



1. The simple sulphate has a taste slightly pungent, and a Simple sul- 

 little bitter, with something metallic. Its crystals, which p ate ' 

 are of no great bulk, are sections of irregular octaedra 



heaped together, of a gooseberry red colour, and unalter- 

 able in the air. By distillation they lose 42 per cent, of 

 water, and are rendered rose-coloured and opako. In this 

 state they can endure a red heat without being decomposed, 

 except in the points that touch the retort. 



2. When sulphate of potash is mixed with the preceding Triple sulphate 

 sulphate, we obtain more bulky crystals, which are rhom- 



boidal cubes. This triple salt is less soluble than the sim- 

 ple sulphate, and loses only 26 per cent, of water by dis- 

 tillation. 



Carbonate. 

 Carbonate of potash produces 40 or 42 hundredth parts Carbonate, 

 of carbonate of cobalt with the simple sulphate. An ex- 

 cess of alkali dissolves a great part of the precipitate^ Boil- 

 ing, or cold water, decomposes this solution. 



Oxide at a Minimum. 



A hundred parts of the carbonate, after the separation Greenish grey 

 of the water and carbonic acid, leave 60 or 62 of greenish 0XI e " 

 grey oxide. To have it very pure, the retort must be as 

 full as possible, and heated gradually. Without these pre- 

 cautions it will be mixed with oxide at a maximum, which 

 yields oxigen gas with muriatic acid, while that which is 

 pure does not yield an atom. 



The grey oxide dissolves with heat in nitric acid, without Heated in the 

 yielding nitrous gas. Heated in contact with air it imme- * Ir b ^ comes 

 diately becomes black ; an oxide of which part is carried and insoluble. 

 to the maximum is easily detected by the application of a 

 weak acid, which dissolves only the oxide at a minimum. 

 Ammonia produces the same separation, as Thenard ob- 

 served. 



Oxide by Precipitation. 

 1. A few drops of nitrate of cobalt dropped into boiling Nitrate preci- 

 water alkalized with potash give a blue precipitate, which plt ^ ted d by pot " 

 ultimately becomes of a rose colour, if the boiling be con- verted into a 

 *uued. In this case a hidrat is formed. jj*™* b - v boU ~ 



2. If 



