298 Analysis of Arsenical Nickel, 



soda throws down at first the arseniate of iron, and then any 

 simple peroxide that may remain, if more muriate of iron was 

 added than was necessary to afford sufficient peroxide of iron to 

 saturate the arsenic acid. The arseniate of iron is yellowish 

 white, the simple peroxide brown-red, showing that no arsenic 

 acid remains in the solution, if the ferrugineous precipitate, after 

 being yellowish white, appears red in the last portions ; and in- 

 deed if this does not happen at first, more of the muriate of iron 

 should be added, till the brown-red precipitate shows itself. All 

 the arsenic acid and oxide of iron being thus got rid of, nothing 

 but nickel «nd eobalt remains in the solution, which must then 

 be separated. The process of M. Laugier answers this purpose 

 completely ; but, as M. Tuputi observes, where it is only desired 

 to procure a quantity of pure oxide of Jiickel, without regard to 

 accuracy of analysis, it is a mivch cheaper and simpler method 

 to add an alkaline subcarbonate to the solution of the two me- 

 tals } which first throws down the pure rose-coloured oxide of 

 cobalt, then a mixture of the two metals, and lastly pure oxide 

 of nickel. When only the latter is left in the solution, it is to 

 be boiled with an alkaline subcarbonate, and the precipitated 

 oxide well washed. 



Arseniate of Nickel. 



To prepare this salt, 1-96 gramme of oxide of nickel was 

 dissolved in muriatic acid, three grammes of arsenic acid in wa- 

 ter were added, and then precipitated by a subcarbonate of alkali, 

 and the whole was filtered and the liquor boiled, to throw down 

 the small quantity of arseniate held in solution by the carbonic 

 acid. The arseniate of nickel thus obtained, weighed after cal- 

 cination 3-91 gr. being exactly double the weight of the oxide 

 of nickel. To recover the remainder of the arsenic acid, one 

 gramme of peroxide of iron in muriatic acid was poured in, and 

 the arseniate of iron was precipitated by an alkali j it weighed 

 l'97gr. of which consequently 0*97 gr. was arsenic acid. A 

 loss of O'OS gr. appears in this operation : nevertheless it may be 

 concluded that arseniate of nickel contains nearly equal parts of 

 acid and oxide — a result confirmed in various ways. 



From the known composition of protoxide of nickel and of 

 arsenic acid, it is obvious that the arseniate of nickel, separated 

 by the carbonates from its solution in acids, is a sub-salt, con- 

 taining one and a half as much base as the neutral arseniates; 

 The same takes place with the arseniates of cobalt, copper, and 

 peroxide of iron obtained in the same way, but not with the ar- 

 seniate of lime precipitated from its acid solutions by a great 

 excess of ammonia. 



Ten grammes of arseniate of nickel heated in a crucible lined 



with 



