118 Experiments' on Niccolanum. [Fe®. 



the light of day or by a candle. The oxide, being allowed to 

 remain for several days under the ammonia, diminished in 

 quantity and became lighter coloured. The solution in ammonia, 

 being drawn oil by a syphon, was clear and pure blue, and was 

 evaporated to dryness without undergoing the smallest change 

 of colourv The residue, after evaporation, was a light green 

 oxide, H'^hich when heated to redness became black, and weighed 

 427 milligrammes (6*58 grains). It dissolved before the blow- 

 pipe in phosphate of soda, and the bead had a blood-red colour 

 while hot, but became honey yellow when cold; and when salt- 

 petre was added gave a bluish coloured bead. In borax it dis- 

 solved with difficulty, and the colour of the bead was reddish 

 brown. The solotion of it in muriatic acid /ormed characte^rs on 

 paper of a green colour^ scarcely perceptible while warm. All 

 these properties show clearly that the oxide examined was pure 

 oxide of nickel. 



(d) The liquid remaining after the precipitation of niccolanum 

 by caustic potash (c ). and the water en^ployed in washing the 

 precipitated oxide, being boiled, assumed a green colour, and a 

 small portion of green oxide precipitated, which was added to 

 the oxide exaniined in the preceding paragraph. The liquid 

 being concentrated to crystallization, and the mother iye mixed 

 with nitrate of silver, it exhibited no trace of arsenic acid. 



(e) The portion of oxide, which the caustic ammonia had left 

 undissolved, was again digested in a fresh quantity of ammonia. 

 The solution became oluish, but exhibited also a shade of red or 

 amethyst, especially v/hen esfeiioioed by candle- light. The 

 ammonia had tiierefore taken up a portion of cobalt, which, by 

 its long continued action, it had brought down to a lower degree 

 of oxydizement, and rendered soluble. By slow evaporation a 

 greei'ish oxide of nickel was obtiiined, and the liquid assumed a 

 bluish colour, but which at last was changed into a reddish. The 

 precipitated oxide, being separated and examined before the 

 blow'pipe with bor^x, exhibited evident marks of containing 

 cobalt. 



(f) As the oxide of cobalt, from the preceding experiments, 

 was found to be soluble in ammonia, and again brought to a 

 minimum of oxydiZement, an attempt was made by a new 

 solution in nsuriatic acid, piecipitating by caustic potash, washing 

 the precipitate, and agitating it with oxymuriate of lime, to 

 render the cobalt again insoluble, till the whole of the nickel 

 was separated from it ; but the attempt did not succeed ; for the 

 solution in ammonia was violet coloured, and contained both 

 oxides. The colour of the oxide changed, in a very short time^ 

 from black to grey. 



(g) As this method of separating the two metals was unsuc- 

 eessiu}^ we had recourse to the method of Proust, by repeated 



