AMMONIA-COBALT BASES. 45 



NITRATE OF LTJTEOCOBALT. 



This beautiful salt is almost invariably obtained during the oxidation of an 

 ammoniacal solution of nitrate of cobalt, and is deposited upon the bottom of the 

 vessel in bright orange crystalline scales. The supernatant liquid is usually red, 

 and contains nitrate of Roseocobalt. The orange-yellow salt is easily purified by 

 re-crystallization. The salt may also be easily prepared from the chloride or sul- 

 phate by double decomposition with nitrate of silver or of baryta. The nitrate of 

 Luteocobalt crystallizes readily in forms which belong to the square prismatic or 

 dimetric system. According to Professor Dana, the dimensions and angles of the 

 crystals are as follows : 



Fig. 19. 

 1 : 1 (over the base) = 110° 20' 

 0:1 = 124° 50' 

 0:3 = 103° 4' 

 3 : 3 (over the base) = 153° 52' 



a = 1.0161 

 O : i (not observed) = 134° 33' 



The crystals are usually small and often very brilliant. The salt is readily 

 soluble in hot water, and separates in small crystals on cooling. Chlorhydric acid 

 throws it down from its solution as a yellow crystalline powder; nitric acid also 

 precipitates it, but sulphuric acid converts it into sulphate with more or less 

 complete decomposition. The nitrate of Luteocobalt is anhydrous, and has the 

 formula 



6NH 3 .Co 2 3 >3N0 5 



as the following analyses show : 



0. 19*72 grs. gave 0.0880 grs. sulphate of cobalt = 16. 98 per cent, cobalt. 

 0.2090 grs. " 0.0928 grs. " " = 16.87 " " 



1.0859 grs, " 0.5151 grs. water = 5.27 per cent, hydrogen. 



0.9126 grs. " 0.4337 grs. " = 5.28 " " 



0.6242 grs. gave 188 c. c. at 11°.5 C. and 772 mra .40 at 11°.94 = 180.56 c. c. at 0° and 760 mm = 

 36.33 per cent, nitrogen. 



0.7394 grs. gave 226 c. c. at 13°.5 



C. and 766"" 



-.05 at 



14° = 



213.29 



c. c. at 0° and 760""" = 



36.23 per cent, nitrogen. 













The formula requires 













Eqs. 



Calculated. 





Mean. 





Found. 



Cobalt . . 2 



17.00 





16.93 





16.98 16.89 



Hydrogen . .18 



5.18 





5.27 





5.27 5.28 



Nitrogen . . 9 



36.31 





37.28 





36.23 36.33 



Fremy and Rogojski deduce the same formula from very imperfect analyses. 

 Heat decomposes the dry nitrate of Luteocobalt with a slight explosion, a black 

 powder of an oxide of cobalt remaining. It may be remarked that the oxygen and 

 hydrogen in this salt are exactly in the ratio to form water. 



