W. Gibbs on the Hexatomie compounds of Cobalt. 193 
was precipitated by potassic dichromate, and the orange-red 
needles obtained recrystallized for analysis; of these crystals 
0°6145 gr. gave 0°7393 gr. CrO, Ba=51°40 per cent Cr,O,. 
07712 gr. gave 0°9277 gr. CrO, Ba=51°40 per cent Cr,0O,. 
0°5615 gr. gave 96°5 c.c. nitrogen (moist) at 15° C. and 763"™-1= 
20°12 per cent nitrogen. 
0°5028 gr. gave 86 c.c. nitrogen (moist) at 15° C. and 763™™1= 
20°05 per cent nitrogen. 
The formula Co,(NH5)(NO,),Cr,0, requires 53°22 per cent 
Cr,0; and 20-67 per cent nitrogen, while the formula of the 
octamin salt, Co,(NH;)NO,),Cr,O;, requires 32°91 per cent 
Cr,O, and 19°30 per cent nitrogen, so that the analyses leave 
no reasonable doubt that the salt was a mixture of a salt of 
| xanthocobalt with a smaller proportion of the corresponding 
salt of the octamin series. 
| . * 
. as the compound Co.(NHs)x(NOz), combines with two atoms of 
‘ chlorine. The structural formulas may be written respectively : 
! ( NH,—NO, 
‘ ( NH,—NO, | NH, —NO, 
ae a co Se 
2 Eso oo eee 
| NH,—NO,; NH,—NO, 
With these formulas we may advantageously compare those 
of chloride of luteocobalt, of Fischer's salt considered as anhy- 
us, and of chloride of xanthocobalt: 
Am. Jour. Sete tarey + saa, Vor. VII, No. 45,—Sept., 1874. 
