1819.] Scientific Intelligence. 145 



g'een, refuses to yield any more crystals of sulphate of nickel. 

 y evaporating it to the requisite consistency, and then setting 

 it aside, a very abundant deposit is made of an apple-green salt, 

 which adheres very firmly to the evaporating dish. 1 took this 

 matter at first, from its colour, to be arseniate of nickel ; but I 

 found it on examination to be a double salt, consisting of sulphate 

 of nickel and arseniate of nickel united together. I endeavoured 

 to get rid of the arsenic acid by dissolving the salt in water and 

 causing a current of sulphuretted hydrogen gas to pass through 

 it as long as any precipitate appeared. By this method I threw 

 down a great deal of arsenic ; but on filtering and evaporating 

 the liquor, it was still converted into an apple-green matter, and 

 of course contained arsenic. I found that when this salt was 

 dissolved in water, the liquid became opaque, owing to a quan- 

 tity of arsenious acid which separated from the salt. The liquid 

 being now filtered to get rid of the arsenious acid, and properly 

 evaporated, yielded a new crop of crystals of sulphate of nickel. 

 These crystals continued to be deposited as long as a single drop 

 of the liquid remained unevaporated. 



By this method may the whole of the nickel in the speiss be 

 obtained in the state of sulphate of nickel. This sulphate is 

 quite free from arsenic or arsenious acids ; for the presence of 

 these acids prevents sulphate of nickel from crystallizing. But 

 for greater security, I dissolve the sulphate of nickel in water, 

 and crystallize a second time. 



The pure sulphate of nickel thus obtained is dissolved in water, 

 and decomposed by carbonate of soda. The carbonate of nickel, 

 when well washed and dried, is a light-green coloured powder. 

 I make it up into balls with a little oil ; enclose these balls in a 

 charcoal crucible, which is put into a hessian crucible, the 

 mouth of which is covered and luted. It is now exposed to 

 the greatest heat that I can raise in a melting furnace for two 

 hours. By this process, I have always obtained a button of pure 

 nickel in the metallic state. 



The nickel thus obtained is hard, but malleable, and very 

 obedient to the magnet. I think it contains a certain propor- 

 tion of carbon in combination with the nickel. The button is 

 usually surrounded with a thin dark shining cuticle, which I take 

 to be a carburet of nickel. 



III. Acetate of Ammonia. 



It does not appear that chemists have hitherto hit upon a 

 method of obtaining this salt in crystals ; at least I find no 

 traces of any such method in the latest chemical works which I 

 have seen, nor indeed any addition to the facts known respecting 

 this salt more than 30 years ago. I conceive, therefore, that it 

 will be acceptable to practical chemists to be put in possession 

 of a method of crystallizing this salt with as much facility as any 



Vol. XIV. N°II. K 



