10 PROCEEDINGS OF THE AMERICAN ACADEMY 



small excess of nitric acid. The cbloro-fluosilicate appears to combine 

 with auric and platinic chlorides to form crystalline salts containing 

 silicic fluoride, titrate of purpureocobalt gives with a solution of 

 fluosilicic acid, SiF^Hj, a beautiful violet-red granular crystalline pre- 

 cipitate, but slightly soluble in cold w^ater. I have not examined this 

 salt; it is probably the normal fluosilicate Co2(NH3)j^,(SiP',;)..,. 



It occurred to rae that the fluorine compounds of the cobaltamines 

 mi"ht offer means of separating certain metallic elements which have 

 hitherto proved intractable by ordinary methods. The numerous ex- 

 periments made with this end in view have not, however, led to really 

 valuable results. I shall therefore content myself by briefly describ- 

 ing in this place a few reactions which will serve as starting-points to 

 those who may be disposed to enter upon this field of investigation. 



Nitrate of croceocobalt gives a fine granular crystalline f-alt with 

 fluosilicic acid, and a beautiful salt in large granular crystals with 

 potassic fluo-titanate, TiF,.K,. Both salts are soluble in much hot 

 water, the solutions yielding large and perhajis measurable crystals. 



Nitrate of xanthocobalt gives very fine granular crystalline salts 

 with fluosilicic acid and potassic fluotitanate. Both salts may be 

 dissolved in a large quantity of hot water, and recrystallized without 

 deC'imposition. 



Sulphate of roseocobalt gave no precipitate with fluosilicic acid or 

 potassic fluosilicate even after long standing ; but a solution of the 

 iodo-sulphate of roseocobalt, Co^(NH3)]„(SO^)^l2, gave with fluosilicic 

 acid a dull violet-red crystalline precipitate very slightly soluble in 

 water. 



Nitrate of luteocobalt gives beautiful granular orange-yellow crys- 

 talline precipitates with fluosilicic acid and solution of potassic fluo- 

 titanate. The fluotitanate is somewhat lighter in coloi- than tiie 

 fluosilicate. Both salts are almost insoluble even in boiling water. 

 Krok * observed that iodo-sulphate of luteocobalt gives a very in- 

 soluble crystalline precipitate with fluosilicic acid. I Had tiiat this 

 salt contains iodine, and it will probably pi-ove to have the formula 

 Co2(NII,,),2(SiF^)2T2. Iodide of luteocobalt gives a beautiful orange 

 crystalline precipitate with potassic fluozirconate, which rt'ijuires a 

 large quantity of boiling water for solution, and may be reci-ystallized 

 without dcconqxisition. Iodide of luteocobalt gives also crystalbne 

 very slightly soluble precipitates with potassic fluotantalate, fluo- 

 niobate, and oxyfluoniobate, not differing from each other, so fiir as I 



* Acta Universit. Lund. 1870. 



