452 Miscellaneous Intelligence. 



In place of the neutral chromate of potash, the solution of 

 the native chromate of iron, acted on by nitre, and neutralized 

 by nitric acid, may be used with the same advantage. — Annales 

 de Chimie, xv. p. 76. 



2. Sulphuret of Chrome. — M. J. L. Lassaigne has succeeded 

 in preparing this substance, by acting on the chloride of chro- 

 mium with sulphur. A chloride is first prepared, by boiling 

 chromic acid with muriatic acid in excess, and evaporating to 

 dryness ; the dry mass is then mixed with five times its weight 

 of sublimed sulphur, and heated to whiteness in a bent glass 

 tube ; a sulphuret of chromium is obtained. The sulphuret is 

 of a blackish grey colour, of an unctuous feel, very light, 

 easily falling to powder, and when rubbed on bodies leaving 

 marks similar to those of plumbago. When heated red in a 

 platinum crucible, it burns like pyrophorus, gives out fumes of 

 sulphurous acid, and a deep-green coloured oxide of chromium 

 remains. Nitric acid does not act readily on it, but aqua- 

 regia dissolve it. It is composed of chromium 100, and sulphur 

 10.54. 



3. Preparation of the Oxide of Chromium. — In consequence of 

 the preceding experiments, M. Lassaigne has devised a new 

 and economical process for the preparation of the green oxide 

 of chromium. It consists in calcining a mixture of equal parts 

 of chromate of potash and sulphur in a close earthen crucible, 

 at a red heat, and in washing the green mass which is produced, 

 to dissolve out the sulphate and sulphuret of potash. The 

 oxide of chromium remains, and by repeated washings is 

 rendered pure. 



It is not necessary that the chromate of potash should be in 

 a crystalline state. The oxide was obtained of an equally fine 

 colour, by calcining sulphur with the produce of the evaporation 

 of the solution of chromate of iron, treated by nitre, to which 

 had previously been added a little sulphuric acid to precipitate 

 the alumine and silex that had been taken up in the operation. 

 — Annales de Chimie, xiv. p. 299. 



