144 Scientific Intelligence. [Aug. 



* # * The specimen of nickel, as far as I could judge from its 

 appearance, was pure. It had the colour, and texture, and 

 malleability, and magnetic properties of pure nickel. I did not 

 consider myself as warranted to apply any chemical test, as I had 

 the specimen to return ; but Dr. Clarke can easily satisfy him- 

 self of its purity by the following method : Nitric acid will readily 

 dissolve it, and form a grass green solution. Ammonia will 

 throw down nothing from it if the nickel be pure. A drop of 

 prussiate of potash will throw down a milk-white precipitate. 

 This precipitate will be reddish if copper be present in the 

 nickel, while it will have a shade of green if the nickel be alloyed 

 with cobalt. 



The specimen of titanium, alluded to by Dr. Clarke, is still in 

 the state of an oxide. The colour of this metal is red. Its 

 oxide does not seem capable of being reduced per se by heat. I 

 have seen specimens of the oxide of titanium melted before ; 

 one which Dr. Clarke sent me some years ago, and another 

 which was melted by a powerful galvanic battery, 1 believe Mr. 

 Children's. The present specimen is precisely similar to the two 

 former ones, neither of which was reduced, as I ascertained by 

 experiment. — T. 



II. On the Method of procuring pure Nickel. 



If Mr. Tennant failed in obtaining pure nickel by the method 

 at which Dr. Clarke hints in the preceding letter, the reason 

 must have been, I conceive, that he was not in possession of a 

 furnace in which he could raise a heat sufficiently strong to melt 

 the metal ; for I have myself obtained pure nickel by this way 

 several times ; and I have seen it obtained also by Dr. Wollaston 

 in the same way. It is to him indeed that I am indebted for the 

 idea of the process. Perhaps a short account of the method 

 which I follow may be of some use to those who wish to procure 

 metallic nickel in a state of sufficient purity. 



I take a quantity of the brittle reddish alloy, well known in 

 commerce by the name of speiss. This alloy is chiefly an arse- 

 niuret of nickel ; though it probably contains also occasionally 

 at least several other metals. Upon the speiss reduced to a 

 coarse powder, I pour a quantity of dilute sulphuric acid, place 

 the mixture in a Wedgewood evaporating dish upon a sand-bath, 

 and add the requisite quantity of nitric acid at intervals to enable 

 the acid to act upon the speiss. By this process, I obtain a 

 deep grass-green liquid, while a considerable quantity of arse- 

 nious acid remains undissolved. The green liquid is carefully 

 decanted off the arsenious acid, and evaporated on the sand-bath 

 till it is sufficiently concentrated to yield crystals. It is then 

 set aside in a cool place. A deposit of beautiful crystals of 

 sulphate of nickel is obtained. By concentrating the liquid still 

 further, more crystals of sulphate of nickel fall ; but after a 

 certain time, the liquid, though its colour continues still a dark 



