290 W. Gibbs on the Hexatomic compounds of Cobalt. 
So far as the empirical formula is concerned, the salt may 
be regarded as a nitrite of purpureocobalt or roseocobalt, 
Co,(NH,), (NO,),+40H,. Its solution gives, however, the 
reactions of salts of xanthocobalt with the greatest distinct- 
ness, and I regard it, therefore, as the normal nitrite of this 
series, with the formula Co,(NH,), ,(NO,),(NO,),440H,. 
Its formation from sulphate of roseocobalt and baric nitrite is 
expressed by the equation : 
Co2(NH,) ,.(SO,),+3BaNO,—Co,(NH,),,(NO,),+350,Ba, 
and from chloride of purpureocobalt and argentic nitrite by the 
equation, 
Co,(NH,),,Cl, +6AgNO, =Co,(NH,),,(NO,),+6AgCL 
The formation of the silver salt of Erdmann’s series, Co,(NH,), 
(NO,),Ag,, is probably due to a secondary action, and may, 
perhaps, be expressed by the equation 
Co,(NH5;), o(NOz)e+2AgNO»=Cog (NH,),(NO,),Ag2+ 
Ammonia-cobalt-nitrate of xanthocobalt—When a solution of 
potassic ammonia-cobalt-nitrite is added to one of nitrate of 
0°5074 gr. gave 0°3172 gr. SO,Co=23-77 per cent cobalt. 
04731 gr. gave 135 ¢.c. nitrogen (moist) at 12° C. and 757°8 mm.= 
33°69 per cent. nitrogen, 
{Co,(NH,),,(NO,.).} (Co,(NH,),(NOz),} 2= 
3Co,(NH,),(NO,),. 
In endeavoring to obtain measurable crystals by allowing 4 
ta r 
formed. 
Oxalate of xanthocobalt.—In the first part of this memoir, i0 
consequence of an oversight, the formula given for the oxalate 
of xanthocobalt contains (old oi ed five atoms of water of crys 
tallization. The salt is really anhydrous, and the anal yses given 
agree with the formula Co,(NH,), ,(NO,),(C,0,),.. The salt 
