THE 

 LONDON, EDINBURGH ano DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



OCTOBER 1851 



XXXVII. On a Class of Ammoniacal Compounds of Cobalt. 

 By Frederic Claudet*. 



WHEN ammonia is added in excess to a solution of proto- 

 chloride of cobalt mixed with four times its weight of 

 chloride of ammonium^ the solution becomes of a dark brown 

 colour without any appearance of a precipitate. In this state the 

 solution rapidly absorbs oxygen from the air ; and on frequently 

 agitating a bottle half-filled with this solution, removing the stop- 

 per from time to time to renew the air, the absorption is much 

 facilitated, and is complete in the space of three or four days, 

 the colour of the liquid changing at the same time from dark 

 brown to an intense violet-red. If the air be replaced in this 

 experiment by pure oxygen gas, the oxidation is still more rapid, 

 and may be completed (if the quantity of solution be not too 

 large) without requiring the removal of the stopper. By boiling 

 this oxidized ammoniacal solution, strongly acidified with hydro- 

 chloric acid, a heavy crimson powder is deposited. A slight 

 effervescence takes place at the same time, due to the evolution 

 of a certain quantity of oxygen, and the liquid becomes nearly 

 colourless owing to the precipitation of the whole of the cobalt 

 in the form of the new compound. The liquid when cold is 

 drawn oif from the red powder, which is washed several times by 

 decantation with distilled water, thrown on a filter and allowed 

 to dry in a warm chamber. The precipitated powder thus ob- 

 tained is nearly pure. Before examination it is, however, neces- 

 sary that it should be crystallized. The powder for this purpose 

 is dissolved in boiling water to which a few drops of hydrochloi^c 

 acid have been added j and on cooling, the salt is deposited in 



* Communicated by the Author. 

 Phil Mag, S, 4. Vol, 2. No. 11. OcU 1851. T 



