156 Proceedings of Indiuna Academy of Science 



definite coinpouiul, iI,.xCo.(.SCN)4x, a iiiixture of several .sucli acids, 

 or an acid of definite formula along with a large excess of HSCN. 

 That upon evaporation the ether solution deposits deep blue crystals 

 having a strong acid reaction makes it probable that a definite acid, 

 H2xCo.(SCN)jx, is present and that it is capable of existence in solid 

 crystalline form. The problem of obtaining this compound sufficiently 

 pure for analysis is being further investigated. 



The conclusion drawn from table 1 of the preceding paper on Vogel's 

 reaction, that the fracti n of cobalt which passes into the ether layer 

 reaches a maximum at moderate concentrations of mineral acid and then 

 decreases as the acid is increased, is clearly verified by the data of 

 table 3 above, as shown in the last column. 



Alkali salts of Thiocyanatocobaltotis Acid. Deep blue double thiocy- 

 anates of cobalt and alkali metals have been prepared in crystalline form 

 by Treadweir and by Rosenheim and Cohn." These investigators agree 

 in assigning to these salts the empirical formula, Co(SCN)l..2RSCN, 

 in which R may be NH„ K or Na, but they differ as to their properties 

 and hydration. By transference experiments Rosenheim and Cohn proved 

 that the blue color was due to a complex anion, Co (SCN),'. Treadwell, 

 working with organic solvents, obtained the potassium and ammonium 

 salts in anhydrous condition and found them to be quickly decomposed 

 by water and even by moist air. Rosenheim and Cohn prepared 12-14% 

 .'olutions of HSCN by action of US on concentrated solutions of Hg- 

 (SCN)i. and by action of this acid on CoCO; prepared cobalt thiocyanate 

 in violet rh:mbic crystals of composition Co(SCN)-.3H.O. By addi- 

 tion of the calculated amounts of the various alkali thiocyanates to 

 aqueous solutions of this salt they obtained in well defined crystalline 

 form the potassium and ammonium salts, each with 4 molecules of 

 water, and the Na and Ba salts each with 8 molecules of water. They 

 found all these salts to be soluble in methyl, ethyl and amyl alcohol and 

 in acetone and that they could be recrystallized from concentrated aque- 

 ous solution without decomposition. They also prepared the anhydrous 

 salts by Treadwell's methods and from aqueous solutions of these ob- 

 tained the hydrated salts without decomposition. It seemed worth while 

 to investigate these discrepant statements. 



A simpler method of preparing the potassium salt and also Co- 

 (SCN):.3H;0 was worked out. The work described below verifies the 

 statements of Rosenheim and Cohn but it was found that the tri-hydrate 

 is the form of the potassium and ammonium salts which is stable in air 

 at the temperature of the laboratory, although, as .stated by Rosenheim 

 and Cohn, the tetra-hydrate separates from aqueous solution. The loss 

 of one molecule of water is not accompanied by any change in the ap- 

 pearance of the crystals. The sodium complex salt was not prepared. 



Experimental. 



To concentrated aqueous solution of CoSOi was added the amount 

 of KSCN calculated to form the double salt and then ethyl alcohol in 



' Z. anoik'. Cher.-... 2fi. ing (1900). 

 - Loc. cit. 



