Scheikunde. — De Heer Ernst Cohen biedt een inededeeling aan 
van den Heer Nil Ratan Dhar : ^^Notes on Cohaltnmmines” . 
(Mede aangeboden door den Heer van Rombuegh). 
In two previons investigations (Zeit. Anorg. Chem. 1913, 80,43; 
84, 224) 1 bad occasion (o stndy certain proporties of tlie cobalt- 
amniines. This note is tbe resiilt of the continnation of tny previons 
work. 
1. Let us consider tlie folio wing series of compounds 
K 
[Co(NH.).] Ci., 
(NH.1 
CL. 
Cl, 
(NO,) J 
L (NO,).J 
7 
L (NO,).J 
Co 
(N0,),_ 
and K, [Co (NO,)j]. For the preparation of 
CL, 
Cl, 
and K 
L (NO,) J 
L (NO,),J 
_ (N0,),_ 
L (NO.)J 
the genera! raethod of procedure is to mix a cobalt salt, ammonium 
chloride, ammonium hydroxide and a uitrite; by this a complex 
cobaltous compound is formed which is turned into the stable cobaltic 
compound by oxidation. The amount of a certain compound which 
will be formed depends on the concentration of the reacting substances 
and on the solubility of the resulting complex compound. If the 
concentration of the nitrite in the.solution is large in comparison 
with the concentrations of ammonium hydroxide and ammonium 
chloride we should expect that several (NOJ gronps would enter 
the complex. 
It is known froni a long time that aquopentammine salts can be 
converted into the corresponding hexammine salts by heating the 
aquo compound with ammonia in a sealed tube or in a bottle under 
pressure. 
I found that if 
(NOJ _ 
CL 
is warmed with a dilute solution 
of sodium or potassium nitrite we get mainly 
could be purified by recrystallisation. 
In a similar way croceo cobalt chloride 
(N0.),_ 
Cl, which 
Co 
(NH3), 
(N0.)._ 
Cl can be 
