1813.] Experiments on Niccolamm. 117 



dowDj which, though mixed with an excess of warm caustic am- 

 monia, was not dissolved. The liquid was colourless, which 

 proved that it contained in solution neither nickel, niccolanum, 

 nor cobalt. It was filtered, and the sal ammoniac evaporated to 

 dryness. During this evaporation more oxide was precipitated, 

 A sufficient quantity of caustic potash was employed to decom- 

 pose th€ vvhole of the sal ammoniac ; the mixture was then dis- 

 solved in water, and a small portion of undissolved oxide re- 

 mained behind. That these different precipitates consisted of 

 the oxide of iron was ascertained by treating them before the 

 blow-pipe with phosphate of ammonia, saltpetre, &c.; but the 

 quantity at the highest estimation did not exceed two milli- 

 grammes (-03 grain Troy). 



(b) A current of sulphureted hydrogen gas was passed through 

 the solution of niccolanum in nitric acid. For some time no 

 change was perceptible, but after the interval of an hour it be- 

 gan to grow muddy, and yellowish flocks were separated, which 

 fell to the bottom of the vessel. These being separated and 

 dried had a blackish brown colour, but their quantity was so 

 small that they could not be weighed. Before the blow-pipe 

 they exhibited the properties of sulphuret of arsenic, and emitted 

 unequivocally the smell of arsenic. Hence it follows, that 

 niccolanum contains a small portion of arsenic ^ but it is quite 

 free from the least trace of copper. 



(c) The solution was exactly saturated with caustic potash. 

 The precipitate which fell was, at the instant of precipitation, of 

 a whitish green colour, but it gradually changed into a light 

 greenish and bluish grey colour, or a mixture of blue and green 

 oxide like what is obtained from a solution of cobalt alloyed with 

 nickel. That portion of the precipitate which attached itself to 

 the sides of the glass, and was not in contact with the liquid, had 

 a light green colour. When diluted with water the precipitate 

 a^ppeared of a light mountain green. It was mixed with water, 

 which was drawn off repeatedly by a syphon, till all the salt dis- 

 appeared. As from the mixed colours of the precipitate, and 

 from several other circumstances, we began to suspect that it was 

 a mixture of the oxides of nickel and cobalt, we made choice of 

 the method proposed by Thenard, in the AUg, Jour, der Ckemie^ 

 vol. iv, p. 284, to separate these metals from each other. For 

 that purpose we prepared a solution of lime in oxymuriatic acid^ 

 and agitated the precipitate in this solution in a well stopped glass 

 flask. It was immediately changed into an oxide, containing 

 more oxygen, and having a black colour. This black oxide was 

 freed from all muriate of lime by washing it with water till the 

 liquor ceased to precipitate nitrate of silver. Caustic ammonia 

 was added in excess ; it assumed a deep blue colour without in- 

 eiining to red or garaet (as Richter alleges) either when seen by 



