158 Proceedings of Indiana Academy of Science 



3. Both the blue complex alkali thiocyanatocobaltites and the pur- 

 ple trihydrate of cobalt thiocyanate can be prepared by double decom- 

 position in aqueous solution starting from the sulfate of cobalt and re- 

 moving alkali sulfates by means of alcohol. This simple method avoids 

 the use of thiocyanic acid which is not easy to prepare in at all con- 

 centrated solution and is rather unstable in aqueous solution. 



4. It is shown that at laboratory temperature the trihydrate, and 

 not the tetrahydrate, is the fonn stable in air for the ammonium and 

 potassium thiocyanatocobaltites. In all other respects the statements 

 of Rosenheim and Cohn were confirmed. Treadwell is in error as to the 

 instability of these salts. That the purple trihydrate of cobalt thiocy- 

 anate changes into the yellow-brown hemihydrate rather rapidly when 

 exposed to the air of an artificially warmed room has not been previously 

 recorded. 



