OF ARTS AND SCIENCES. 9 



3.Co,(NH3),o(NO,)«+3Co,(NO,)„Na„=|Co,(NIl3)„.(NO,).j3 

 |Co,(NO,)i.J,+18NaN08+2Co(NO,)2+2NO,. 



I .shall allude to its composition again, when speaking of the metameric 

 compoiiiuls of the cohaltaniines. 



The salt described is not the only one which is formed by the action 

 of a solution of Co^(NO^),2Nag on nitrate of purpureocobalt. In sev- 

 eral experiments I obtained an orange-red gi'anular salt readily soluble 

 in cold water. The solution of this salt gave with nitrate of luteo- 

 cobalt a beautiful crystalline precipitate of 



|Co,(NH3X,nCo,(NO,),J. 



With thallous nitrate it gave the characteristic scarlet salt Co.,(NO^)|2 

 Tly. On the other hand, it gave all the reactions of the salts of 

 xanthocobalt with great distinctness, including the highly characteris- 

 tic crystalline ferrocyanide. This salt could in no way be distinguished 

 from one obtained by the action of Co2(NO^),2Nay upon sulphate of 

 roseocobalt which, as I shall show, has the formula • — 



lCo2(NH3),„nC02(N02),J or Co,{^R,),,(^0,),-{-Co,(m,),. 



In acting upon solutions of purpureocobalt with solutions of cobalto- 

 nitrite of sodium in excess of sodic nitrite, it often happens that 

 neither of the salts above described is obtained in appreciable quantity, 

 but only nitrate of xanthocobalt and cobaltic salts formed by a total 

 reduction of the cobaltamines. It is therefore important to avoid an 

 excess of sodic nitrite as much as possible. 



Chloro-JlaosiUcate. — When a hot solution of chloride of purpureo- 

 cobalt containing a few drops of free chlorhydric acid is poured into a 

 hot solution of fluosilicate of zinc, no precipitate is produced at first, 

 but after a time a beautiful violet-red crystalline salt separates. This 

 salt is very slightly soluble in cold water, but dissolves with a violet 

 tint in a large quantity of boiling water ; it is readily soluble in a hot 

 solution of sodic carbonate. It is decomposed very quietly by heat, 

 giving off white condensible vapors, and leaving a dull violet residue. 

 Of this salt : — 



0-6379 gr. gave 0-2861 gr. SO.Co = \l-\0% cobalt. 

 0-8221 gr. gave 0-2479 gr. silver =z 9-91% chlorine. 



The formula Co2(NH3)io(SiF6),Cl,,4-30H2 requires 16-93% cobalt, 

 and 10-18% chlorine. 



The determination of the chlorine was made by dissolving the salt in 

 sodic carbonate, adding an excess of argentic nitrate, and afterwaid a 



