OF ARTS AND SCIENCES. 9 



solved and again crystallized without decomposition. In appearance 

 and solubility it can hardly be distinguished from the corresponding 

 salt of xauthocobalt, 



Co,(NH3),„(NO,),(CrA)2- 

 The formula of this salt is : — 



Co,(NH3)3(NO,),Cr,0,. 

 0-5604 gr. gave 0-4315 gr. BaCrO^ = o2-91 per cent Cr^O^. 



The formula requires 33-06 per cent. The determination of CrO^ and 

 Cr20j., in this and similar compounds containing NO^, can be effected 

 more accurately by means of a baric salt than by mercurous nitrate, 

 since the nitrous compound always reduces a little chromic acid to 

 chromic sesquioxide. 



Platino-chloride. — A solution of sodic platino-chloride, PtCl^Na^, 

 produces in one of the new nitrate after a time fine orange-brown 

 prismatic crystals, which, however, cannot easily be recrystallized 

 without decomposition. The crystals were washed with cold water, 

 dried by pressure, and then over sulphuric acid. The analysis was 

 made by boiling the salt with zinc and dilute sulphui-ic acid, filtering 

 off and weighing the reduced platinum and determining the chlorine 

 in the filtrate by silver. In another portion of the salt the platinum 

 and cobalt were determined together by gentle ignition in a current of 

 hydi'ogen gas. In this manner, 



0-3959 gr. gave 0-0921 gr. platinum and 0-3016 gr. silver = 23*26 per 



cent platinum and 25-04 per cent chlorine. 

 0-4459 gr. gave 0-1652 gr. platinum and cobalt = 37-04 per cent. 



Subtracting 23-26 per cent platinum from this, we have 13-78 per 



cent cobalt. 



Calculated. Found. 



Cobalt 2 13-91 13-78 



Chlorine 6 25-12 25-04 



Platinum 1 23-23 23-26 



The formula of this salt is therefore: — ■ 



Co,(NH3),(NO,),Cl, + PtCl,. 



Auro-chloride. — A solution of auro-chloride of sodium, AuCl^Na, 

 produces immediately in one of the octamin nitrate a beautiful 

 crystalline precipitate, with a fine canary-yellow color and silky lustre. 

 Small quantities of this salt may be dissolved in boiling water without 

 decomposition, but it is very difficult to recrystallize it without great 

 loss from the reduction of the gold. When boiled for a short time the 



