PURIFICATION OF NICKEL. 



wliole of the solution with caustic potash. T then treated Precipitate 



treated 

 auimon 



the precipitate, after it was well washed, with dilute am- ^^'^^^^ ^' 



monia, the proportion of which I increased, as long as the 

 sapphire blue colour produced was increased in intensity. 

 After macerating- some time, I filLered. The undissolved Resitlunm -^k- 

 portion had acquired a deep green colour, similar to the ^"'X^" ''.' f^*" 

 fine green of Scheele ; and being treated with weak muri- 

 atic acid, it immediately became black, and dissolved, giv- 

 ing oiit oximuriatic acid gas, and imparting to the acid a 

 fine pure rose colour. Tt was ther(?fore oxide of cobalt at 

 a maximum, which could not redissolve in the ammouia, 

 as Mr, Thenard had observed. The ammoniacal solution^, 

 evaporated to dryness, let fall a light green powder, 

 which comported itself as pure oxide of nickel with every 

 reagent. 



On the successive examination of the other two preci pi- Precipitate a$ 

 tates obtained by sulphuretted hidrogen, they were found fio^J'^l-ff^^ 

 to agree, except in the proportions, with the former. In only in ^pfs- 

 fhe last the quantity of cobalt was scarcely perceptible. P*^*^'^^^' 

 The second contained more than a tenth of arsenic in the 

 state of an oxid* not sulphuretted, which might be extracted 

 by boiling water alone. The first contained much more 

 nickel than the others. By the different processes which I 

 employed to analyse the precipitates I constantly found sul- 

 phur, originating from the sulphuretted hidrogen, arsenic, 

 nickel, cobalt, and not an atom of copper. This did not No copper. 

 surprise me, because I knew, that some of these oi'es con- 

 tain none: but what really puzzled me was, to account for What cowls 

 the precipitation of the nickel and cobalt by the snlphnret- ^^''-^f^'^^^ ^,^^ 

 ted hidrogen. I thought at first this was owing to the pro- the nickel a»* 



<*ess I had followed ; but I was completely undeceived, after '^■^^^}^ ^V ** 



. . suiphurctteA 



'having analysed three specimens taken from dilFcrent col- hidrogen! 



iections, and labelled " sulphurtt of copper and arsenic 

 obtained in the purification of nickel." These sulphurets 

 were of the same nature as mine, only one of them con- 

 tained in addition a little copper ; yet they were produced 

 by processes, in which alkali had not been employed for 

 the separation of the arseniates of iron and cobalt as in 

 mine. Obliged to look for some other source of the fact, I 

 firmed a series of conjectures, and made experiments a-c- 



cordingij. 



