286 W. Gibbs on the Hexatomic compounds of Cobalt. 
As the chloride and nitrate of xanthocobalt are capable of 
uniting directly to form the chloro-nitrate above described, it 
might be supposed that the two salts are isomorphous, and, 
therefore, crystallize together in all proportions. According to 
of Dana's measurements, cited in the first part of this 
memoir, nitrate of xanthocobalt crystallizes in forms belong- 
ing to the dimetric or square prismatic system. Prof. Cooke 
has kindly determined the form of the corresponding chloride, 
and finds that the crystals are either trimetric or monoclinic. 
The chloro-nitrate cannot, therefore, be regarded as a mixture 
of two isomorphous salts. 
Finally, salts of xanthocobalt are formed by the action of 
Fischer’s salt, Co,(NO,),,K,, upon salts of purpureocobalt and 
roseocobalt. hen, for instance, chloride of purpureocobalt 
is dissolved in boiling water, with a little free acetic or chlor- 
hydric acid, and Co,(NO,),,K, is added, in small portions at 
a time, the violet color of the salt gradually disappears as the 
boiling continues, and the solution finally assumes a fine orange- 
brown tint. The filtered solution gives on cooling fine crystals 
of chloride of xanthocubalt, the reaction being probably ex- 
pressed by the equation 
Co,(NO,),2K,+43Co,(NH,), oCl,= 3Co,(NH;),.(NO,)2Cl, + 
6KC14+200(NO,),+2N0,. 
During the boiling red vapors are given off. In one experi- 
ment the chloride of xanthocobalt formed was analyzed, with 
the following results : 
0°5027 gr. gave 0°2987 gr. SO,Co= 22°62 per cent cobalt. 
0°7616 gr. gave 0°6351 gr. silver —27-35 per cent chlorine. 
The formula Co,(NH,), ,(NO,),Cl, requires 22°52 per cent 
cobalt and 27-09 per cent chlorine. The salt gave all the reac- 
tions of the chloride. 
. 
ecamin series. I have already mentioned its occurrence 
upon chloride of purpureocobalt. hen nitrate of xantho- 
cobalt is boiled with potassic nitrite and a little acetic acid, 
Fischer’s salt is formed in abundance, and the nitrate is gradu- 
ally decomposed, without formation of any other product which 
I could detect. 
Chromate-——When neutral potassic chromate is added to a 
solution of nitrate of xanthocobalt, a beautiful yellow crystal- 
line precipitate is thrown down, which may be washed with 
cold water, in which it is but slightly soluble. Hot water also 
: ves age salt in very small quantity. The chromate has 
ormul s 
