12 PROCEEDINGS OF THE AMERICAN ACADEMY 



ROSEOCOBALT. 



Sulphates of Roseocohalt. — In our joint memoir Genth and I have 

 stated that when a mixture of cobaltic sulphate and ammonia is ex- 

 posed to the air for some time three different salts are sometimes 

 formed, one of which is readily soluble in water, giving characteristic 

 reactions different from those of the normal sul})hate, while a second 

 salt dissolves in warm water, and gives orange-red crystals. 1 propose 

 now to give the results of my further study of these salts. 



Soluble Sulphate of Roseocohalt. — Since the jjublication of the 

 memoir above mentioned, this salt has been studied by Braun, who 

 appears not to have been aware of its previous discovery by Genth 

 and myself. Braun prepared it by adding sulphuric acid to an oxi- 

 dized solution of ammonia and cobaltic sulphate and precipitating the 

 solution with alcohol. In this manner he obtained a rose-red crystal- 

 line powder, which on analysis gave the formula of the ordinary sul- 

 phate, first correctly analyzed by Genth and myself, Co2(NH3),p 

 (S0J.j-}-<''0H2, but which was readily soluble in water, with a cherry- 

 red color. My more recent investigations fully confirm Braun's 

 results as regai-ds the solubilitj' of this salt, which I have, however, 

 obtained by simply washing the oxidized dry mass of sulphates with 

 cold water in repeated small quantities. To fully estiiblish the differ- 

 ence between this salt and the ordinary sulphate, I determined the 

 solubility of the last-named quantitatively. Of the ordinary sulphate, 

 11-6205 gr. of a neutral solution saturated at 27*^0 gave on evapora- 

 tion 0-1967 gr. of the crystalline sulphate = 1-699^. 



The soluble sulphate recpiires between one and two parts of cold 

 water for solution, as nearly as I could judge, my salt containing small 

 portions of animonic and cobaltic sulphates. The reactions of the solu- 

 ble sulphate differ so slightly from those of the ordinary sulphate, that 

 I do not regard the statement made by Genth and myself as fully 

 confirmed by further experience, and believe that the sail with whirh 

 our experiments were made contained small portions of the yellow 

 sulphate presently to be described. On the other hand, the derivatives 

 of the soluble sulphate appeared in many cases to be more soluble 

 than the corresponding salts prepared from the ordinary sulphate. 



Want of material and of proper fiicilities for work have prevented 

 me from examining the subject with the requisite care and tliorough- 

 ness. In what follows, however, I have in each Case specified which 

 of the two red sulphates was employed. 



