OP ARTS AND SCIENCES. 15 



unfortunately with but very scanty details. I attribute to this salt 



the formula 



f NH3-NO2 

 I NH,-N02 



Co, } ?;&-?s^ 



-"2 



NH,-N02 

 NH3-NO2 



and consider it to be the nitrous representative of the hexamin Cog 



(NH.,)g. I have not succeeded in obtaining from it other members of 



the same series ; but it is, to say the least, probable that the dichro- 



cobalt-chloride of Fr. Rose,* Co2(NH3)6Clg-|-20H2, represents the 



corresponding chloride. Kiiuzel f has described a sulphite to which he 



attributes the formula 



Co2(NH3),(S03)3+OH„ 



but according to Geuther J this formula must be doubled, the salt 

 belonofinof to the dodecamin or luteocobalt series, with the formula 



Co2(NH3),2(S03), + €02(803)3 + 2OH2. 



Erdmann's hexamin salt is of special interest, because, as I shall 

 show, it forms the first term in a remarkable series of metameric 

 bodies : its formation under the circumstances may with great proba 

 bility be expressed by the equation 



2C0CI., + lONH, . NO2 + 30 = Co2(NH3),(N02)6 + 4NH,C1 + 



30H2-f4N02, 



as the salt is not formed immediately, but only after absorption of 

 oxygen from the air. The formation of Erdmann's ammonium salt 

 may in like manner be represented by the equation 



2C0CI2+ lONH,. NO2+ 20 = Co,(NH3),(N02)8(NH,)2+ 



4NH,C1 + 2OH2, 

 the presence of oxygen being necessary in this case also. 



In another experiment I obtained no hexamin nitrite, but only Erd- 

 mann's ammonium salt and the two salts described by Sadtler, and to 

 which he gave respectively the formulas: — 



Co2(N02)io(NHJ, + 20H2, 



Co2(N02)i2(NHJe + 20H2. 



These last salts were formed in considerable quantity mixed together as 



a yellow sparingly soluble crystalline powder, when a strong solution 



* Untersuchungen iiber ammoniakalische Kobalt-Verbindungen. Heidelberg, 

 1871. 

 t Journal fiir prakt. Chemie, 72, p. 209. J Ann. de Pharmacie, 128, p. 127. 



