12 RESEARCHES ON THE 



The sulphate of Roseocobalt is, however, not always the only salt formed under 

 these circumstances. In some cases in which the ammoniacal liquid was allowed 

 to stand several months until there remained only a dry mass of red crystals, 

 warm water dissolved out a red salt in small quantity, much more soluble than 

 the sulphate of Roseocobalt, and giving different and very characteristic reactions. 

 In other cases, and especially when a little chloride of cobalt was originally present, 

 warm water dissolved out another sulphate, crystallizing in octahedra of an 

 orange-red color, the examination of which is not yet complete. 



We are unable to confirm Fremy's assertion that sulphuric acid precipitates from 

 oxidized ammoniacal solutions of sulphate of cobalt, an acid sulphate of Roseo- 

 cobalt, having the formula 



5NH 3 .Co 2 3J 5S0 3 +5HO. 



The salt precipitated under these circumstances is merely the neutral sulphate, 

 as repeated analyses have shown, and as the crystalline form at once proves. The 

 formula of the neutral sulphate is 



5NH 3 .Co 2 3 ,3S0 3 +5HO 



as the following analyses show : 



0.8160 grs. gave 0.3800 grs. sulphate of cobalt = 11.12 per cent, cobalt. 



0.8212 grs. gave 0.3869 grs. " " = IT. 79 " 



0.2160 grs. gave 0.2908 grs. sulphate of baryta = 36.11 per cent, sulphuric acid. 



0.5131 grs. gave 0.6014 grs. " " = 36.38 " " " 



1.4925 grs. gave 0.8250 grs. water = 6.14 " hydrogen. 



1.2840 grs. gave 0.1109 grs. " = 6.15 " 



1.2108 grs. gave 220.5 c. c. nitrogen at 18°.4 C. and 161"™.23 (at 18°.9) = 201.91 c. c. at 0° 



and 160""" = 20.95 per cent, nitrogen. 

 1.0404 grs. gave 194.2 c. c. nitrogen at 20°.5 C. and 154""".31 (at 20°.5) = 114.61 c. c. at 0° 



and 160'"" 1 = 21.08 per cent, nitrogen. 



The formula as above stated requires 





Eqs. 



Calculated. 



Found. 



Mean. 



Cobalt 



2 



59.0 



11.11 



11.12 



11.19 



11.15 



Sulphuric acid 



3 



120.0 



36.03 



36.11 



36.38 



36.24 



Hydrogen 



20 



20.0 



6.00 



6.14 



6.15 



6.14 



Nitrogen . 



5 



10.0 



21.02 



■ 20.95 



21.08 



21.01 



Oxygen . 



8 



64.0 



19.24 







18.86 





333.0 



100.00 



100.00 



The sulphate of Roseocobalt has a fine cherry-red color. The light reflected from 

 a layer of the crystals when analyzed by the dichroscopic lens, gives a rose-red 

 ordinary, and an orange-red extraordinary image. The dichroism is very distinct. 

 In this, as in our other observations upon dichroism, the reflected rays examined 

 made an angle of about 60° with the normal, but no material variations of color 

 could be observed by changing the angle of incidence. The exact color of the 

 crystals is, according to Chevreul, the second red 2-10ths. The crystals of sulphate 

 of Roseocobalt belong to the dimetric or square prismatic system, as determined 



