on the Ammonia'Cobalt Bases. . 93 



$ 



ate of ammonia are given off The liquid gradually assumes a 

 dark brown-yellow color, and frequently deposits an abundance 

 of crystals during the passage of the current of gas. Ammonia 

 must be added ixom time to time, so as to keep the solution 



strongly alkaline, and prevent the appearance of red vapors at 



the surface of the liquid. It is not necessary to apply heat, as 

 the temperature rises from the absorption of the gas. AVheu 

 the operation is over, which is indicated by the color of the liquid, 

 the solution may be filtered and allowed to evaporate spontane- 

 ously, when a mass of brown-yellow crystals is obtained. These 

 may be purified by re-solution in hot-water with addition of a 

 few drops of acetic acid and re-crystallization. 



This method of preparing the salt is a convenient one, and 

 large quantities may be prepared in a few hours. The time re- 

 quired for the completion of the oxydation depends upon the 

 quantity of sulphate of cobalt employed, and may last from one 

 to twelve hours. It is best to employ a rapid current of the 

 gas. The formation of the sulphate of Xanthocobalt, under 

 these circumstances, may be represented by the equation 



2CoO, S03+5NH3-j-X03=N02.5NH3.Co203, 2SO3 



if we suppose the oxj^dizing agent to be XO3. If, however^ we 

 consider the active agent to be NO 4, we may represent the ac- 

 tion by the equation 



2C0O, S03-|-6Xn3+2N04+HO=N02.5NH3.Coa08, 2SO3+ 



NH4O, NO5. 



A large quantity of free nitrite of ammonia is always formed 

 during the process, as "we believe, by the direct action of NO 3 

 upon ammonia and water. The addition of an acid to the 

 mother liquor fi^om wbich the sulphate has crystallized, produces 

 an active effervescence arising from the decomposition of the 

 nitrite of ammonia. 



The process which we have indicated has generally proved 

 perfectly satisfactory in preparing the sulphate. It is proper to 

 state, however, that in some experiments, made for the purpose 

 of revision, we obtained by the process above given no sulphate 

 of Xanthocobalt, but only the nitrate. The cause of this we 

 are at present unable to assign, and further experiments are 

 wanting to explain so unexpected a result. 



The sulphate of Xanthocobalt crystallizes in thin plates, the 

 form of which we have not been able to determine; they appear 

 to belong to the right rhombic system. The crystals have a fine 

 brown-yellow color, which, however, we cannot define by means 

 of the chromatic scale. The salt is rather soluble in bot, but 

 much less soluble in cold water. Heat readily decomposes the 

 neutral solution, a black powder being thrown down, w^hile am- 

 monia is given off. The dry salt is decomposed like the chlorid. 



