124 W. Gibbs on the Hexatomic compounds of Cobalt. 
effected by boiling the salt with zinc as in the case of the 
platinum salt, and determining the chlorine in the filtrate b 
silver, but the gold precipitated was found to contain muc 
metallic cobalt. Another analysis was made by simply heating 
with sulphuric acid, precisely as in the process which Gen 
and myself introduced for the determination of cobalt in these 
salts and then washing and weighing the gold. This method 
was found to give excellent results. In this manner, 
0°4791 gr. gave 0°3697 gr. silver= 25°36 per cent chlorine. 
0°3942 gr. gave 0°2483 gr. Au+ CoSO, = 0°1391 gr. gold, and by 
difference 0°1092 gr. CoSO, = 10°54 per cent cobalt and 35°30 
per cent gold. 
Calculated. Found. 
Cobalt 2 10°57 10°54 
Gold : 2 35°30 35°30 
Chlorine 8 25°44 25°36 
The formula of the salt is therefore 
' Co,(NH,),(NO,),Cl, + 2AuCl,. 
(old style) Co,0,2NH,, 3NO,+KO,NO,. 
In modern notation the formula of Erdmann’s salt may be 
written Co,(NH,),(NO,),K,. 
Erdmann states that the potassium in this salt may be replaced 
by other metals, and describes the corresponding ammonium 
and silver salts. These compounds are especially interesting; 
because they hold an intermediate position between the two 
series represented respectively by the terms 
Co.(NH,),2Cl, and Co,(NO,),,K,. 
I propose therefore to speak of them more in detail hereafter, 
and to confine myself at present to their relations to the salts 
of the octamin series, 
When a solution of Erdmann’s salt, Co,(NH,), (NO,),K., i8 
added to one of the octamin nitrate, a beautiful crystalline 
ite aa is fgrmed, which after washing with cold water may 
e redissolved in hot water and then separates in fine orange 
yellow granular crystals. The equation representing the reac 
tion is here 
Co,(NH,),(NO,),(NO,), +Co,(NH,),(NO,),.K,=2KNOs+ 
Co,(NH,),(NO,),(Co,(NH,),(NO,),)”. 
* Journal fiir prakt. Chemie, xcvii, 385. 
