IG PROCEEDINGS OF THE AMERICAN ACADEMY 



low nitrate gave a beautiful orange-yellow crystalline precipitate with 

 excess of potassic iodide. 

 Of ili(> yellow chloride, — 



0-4187 gr. gave 0-2430 gr. SO, Co = 22-09^ cobalt. 



The formida Co./NII.5),„Cle4-20H,, which is that of the ordinary red 

 modification, requires 21-97% cobalt. 



The results above mentioned, together with the analyses of the jiold 

 and platinum salts to be described, are confessedly incomplete, but are 

 all wliic-h I could obtain with the very small amount of material — less 

 than five grammes of tlie sulphate — at my disposal. I regard them 

 as rendering it extremely probable tiiat there is an extensive series of 

 yellow salts isomeric with the ordinary salts of roseocobalt, but differ- 

 ing from them in color, solubility, and perhaps other particulars. It 

 seems not impossible that the so-called xanthocobalt salts belong to 

 tliis series, as I find that when the beautiful scarlet crystalline iodo- 

 sulphate of roseocobalt is treated with argentic nitrite, a cherry-red 

 solution is obtained, which must contain a salt having the formula, 

 Co.,(NH3)jg(NO^,).^(SOj25 since we have the reaction expressed by the 

 equation 



Co,(NII,)io(SO,) J,^2AgN0, = Co,(NH3),„(NO,),(SO,),+2AgI, 



and since the red solution on boiling with a few drops of acetic acid 

 readily passes into the ordinai-y sulphate of xanthocobalt. 



The salts of the yellow modification of roseocobalt at present more 

 or less perfectly analyzed and described are as follows : — 



Chloride, Co,(NH,),oCl,;+20H, 



Kitrate, Co,(NH,),o(NO,),+3bH, 



Siilphate, Co,(NH,),„(SOJ.3+oOH, 



Sulphato-ohlorplatinate, Co,(NH3),„(SOJ,Cl,+PtCl, 



Sulphato-ciiloro-aurate, Co,(NH3),„(SO,),Cl.,-|-2AuCl,,-f 40II,. 



I may remark in this connection, that rhodium forms two series of 

 salts, one of which is red, and the other yellow, and that the chloride 

 of Claus's base, Rh,(NH.j),„Cl,;. wliieh is yellow, unlike the well-de- 

 fined double chlorides containing Rh^.Cl,;, may be the true analogue of 

 the yellow modification of Co,(NH,),„Cl,,+20Fl2. 



C/ihrplfifinn/e. — When the soluble sulphate of roseocobalt is con- 

 verted into nitrate by double decomposition with baric nitrate, and 

 chlorplatinate of sodium is a<lded, a salt separates in dark-red maniil- 

 Jary crystalline crusts, which may be regarded as the normal i>laiiiium 

 salt of this series. The salt, like most of its congeners, is much more 



