16 PROCEEDINGS OF THE AMERICAN ACADEMY 



low nitrate gave a beautiful orange-yellow crystalline precipitate with 

 excess of potassic iodide. 

 Of the yellow chloride, — 



0-4187 gr. gave 0-2430 gr. 80^ Co = 22-09% cobalt. 



The formula Co2(NH3)joCl6+20H2, which is that of the oudinary red 

 modification, requires 2\-^l ^fo cobalt. 



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

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

 all which I could obtain with the very small amount of material — less 

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

 as rendering it extremely probable that 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 

 this 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.,(NHo)jq(N02)2(SO^)2, since we have the reaction expressed by the 

 equation 

 Co,(NH3),„(SOJ J,-h2AgN0, = Co,(NH3),„(NO,),(SO,),+2AgI, 



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

 readily passes into the ordinary sulphate of xanthocobalt. 



The salts of the yellow modification of roseocobalt at present more 

 or less perfectly analyzed and described are as follows : — 



Chloride, Co2(NH,),oCl,+20H2 



Nitrate, Co,(NH,)„(NO,),+3bH2 



Sulphate, Co2(NII,),„(!^0,),4-50H2' 



Sulphato-chlorplatinate, Co.(NH3),„(SO^),Cl,-f-PtCl^ 



Suljihato-chloro-aurate, Co,^(NH„),„(SO,)XC-|-2AuCl3-|-40H,. 



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.,(Nri„)„|Cl,;, which is yellow, unlike the well-de- 

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

 the yellow modification of Co,(NH3),oClg+20H,,. 



CItlorphitinate. — When the soluble suli)hate of roseocobalt is con- 

 verted into nitrate by double decomposition with baric nitrate, and 

 chlorplatinate of sodium is added, a salt separates in dark-red mamil- 

 lary crystalline crusts, which may be regarded as the normal platinum 

 salt of this series. The salt, like most of its congeners, is much moi-e 



