On the Separation of Nickel from Cvlalt, 107 



i^^ill appear insufficient to those who know that the oxide 

 of nickel, mixed even with many hundred times its weight 

 of cobalt, does not experience any sensible change of co- 

 lour in its precipitations, nor in its solutions with ammonia; 

 and besides, he has not pointed out the means by which he 

 was convinced that the oxide obtained in the residuum of 

 the solution in the sulphuric acid was an oxide of cobalt. 

 The vague precept, to heat the oxide obtained, without 

 giving the least information on the degree of heat ; the 

 uncertaintv in which he leaves us respecting the sulphuric 

 acid of which he made use; all these circumstances throw 

 upon the exactness of the indicated process a doubt which 

 the following experiments alone will be able to clear up. 



1. A portion of oxide of carbonic nickel A, was exposed, 

 during an hour, to a violent tire nearly of a white heat. The 

 oxide, when yet warm, was brownish yellow. After cool- 

 ing it took a gray colour inclining to yellow, but not en- 

 tirely so. The oxide of nickel obtained by the evaporation 

 A 4, having been treated in the same manner, was yet a 

 little more gray than the preceding. The oxide of carbonic 

 nickel was again exposed, for half an hour more, to a white 

 jheat : while hot it was yellow inclining to brownish, but 

 when cold it was gray inclining to a brownish yellow. 



2. Thirty grains of this torrified oxide were kept some 

 hours in digestion with ninety grains of pure sulphuric acid 

 of the specific gravity of l-8()0. Having been afterwards 

 heated, the mass swelled up with a iioisy ebullition, and pre- 

 sented a yellow substance inclining to green. By ebullition 

 with a halt-ounce of water it was dissolved, leaving nearly a 

 grain of powder of a gray yellow, which proved to be oxide 

 of nickel mixed with cobalt, and a little impurity. I ob- 

 tained exactly the same result, with the same appearances, 

 in treating a second time in the same manner, and with 

 00 grains of concentrated sulphuric acid, 35 grains of oxide 

 of nickel, which I had obtained by heating briskly, even 

 to redness, Co grains of nitrate of ammoniacal nickel pre- 

 pared by evaporation. By heating the same oxide to white- 

 ness, in a fire urged with bellows, for half an hour^ I did not 

 .obtain a yellow mass, but one of yellowish gray, inclining 

 a little to green, which acted with the sulphuric acid, as i 

 have formerly stated. 



3. I repeated afterwards the same experiment with sul- 

 phuric acid weakened. 16O grains of oxide of carbonic 

 nickel were exposed, during a lialf-hour, to a very violent 

 white licat; after which they still weighed 73 grains. Thi;? 



N 3 substance 



