192 W. Gibbs on the Hexatomic compounds of Cobalt. 
as the salt is not formed immediately, but only after absorption 
of oxygen from the air. The formation o ; 
nium salt may in like manner be represented by the equation: 
200Cl,-+8NH, .NO, +20=Co,(NH,),(NO,),+4NH,Cl+ 
20H,, 
In another experiment I obtained no hexamin nitrite, but 
only Erdmann’s ammonium salt and the two salts described by 
Sadtler, and to which he gave respectively the formulas: 
Co2(NO2),.(NH,),+20H, 
Co,(NO,),.(NH,),.+20H,. 
These last salts were found in considerable quantity mixed 
together as a yellow sparingly soluble crystalline powder, when 
represented by the equations: 
2C0Cl,+-10NH,. NO,+30=Co,(NO,) o(N Hy) s+ 6NH,+30H, 
2CoCl,+12NH,.NO,+30=Co,(NO,),.(NH,),+-8NH,+ 30H: 
Professor Sadtler has shown that in these cases also an absorp- 
tion of oxygen from the air takes place. When a solution of 
ammonic nitrite is added to a strong alcoholic solution of cobaltic 
chloride, Erdmann’s ammonium salt, Co,(NH,)4(NOz)a(NH4)2, 18 
chiefly formed, and only a small quantity of the four and six-atom , 
salts. The compound formed crystallizes from the alcoholic 
solution in very beautiful and well defined prismatic forms. 
From the above it will be seen that at least four distinct 
compounds are formed by the action of ammonic nitrite upon 
solutions of cobaltic chloride in presence of a weak acid and 
of the oxygen of the air. It is at least probable that all four 
are formed at the same time, though in varying proportions. 
I have already shown that, in the presence of free ammonia and 
of ammonic nitrate, cobaltic chloride and ammonic nitrite yield 
the nitrate of the octamin series. Of the action of ammonic 
nitrite upon cobaltic salts in the presence of free ammonia, I 
shall speak in treating of the formation of the salts of xantho- 
cobalt. 
7. I have stated above that Erdmann obtained the hexamin 
have noticed. Small quantities of salts of the octamin series 
are also formed. The filtered solution obtained in this reaction 
