M. Deville on the Preparation of the Metals. 113 



whicli belong to the cubic system. They are very hard, and 

 resist the action of aqua regia. Many alloys of chromium 

 with other metals possess the hardness of the former, and, like 

 it, resist the strongest acids. An alloy of chromium and iron 

 was obtained by reducing chrome iron ore with charcoal, and 

 also by the action of iron upon oxide of chromium. This alloy 

 often crystallizes in long needles. It resembles cast iron; it 

 scratches the hardest bodies, even steel. Green oxide of chro- 

 mium melts in a blast-furnace, and then forms a black crystal- 

 line mass ; it scratches quartz and steel with ease. 



St.-ClaireDeville*,adverting to his previous researchesf on this 

 subject, points out that by the method of Brunner the presence 

 of impurities is not excluded. Most sodium contains carbon, 

 and being porous, encloses much rock-oil in its pores. Silicon 

 would also infallibly be reduced from the substance of the Hes- 

 sian crucible by means of sodium. That the manganese pre- 

 pared by Brunner is more fusible, and decomposes water less 

 readily than that of Deville, may be hence explained. 



At a red heat sodium attacks porcelain energetically, setting 

 silicon free ; and metals prepared in vessels of porcelain would 

 always be likely to contain silicon. Fremy's chromium may 

 therefore have contained silicon, and this might explain the dif- 

 ferences between this chromium and that prepared by Deville 

 by reduction from the oxide in lime-crucibles. The latter, as 

 well as that which Bunsen prepared by electrolysis, dissolve easily 

 in hydrochloric acid, while that of Fremy resists the action of 

 aqua regia. 



Deville discusses the conditions of preparing metals free from 

 impurities, and points out the advantages presented by the mode 

 of reducing the oxide mixed with an insufBcient quantity of 

 charcoal in a lime-crucible. In this case the lime absorbs the 

 excess of oxide. Debray and himself have found that platinum 

 prepared in small lime-crucibles has quite a different appearance 

 to the ordinary metal, because it has been deprived of the osmium 

 and the silicon which the latter always contains. 



The application of sodium in preparing the metals is advan- 

 tageous in cases in which it is wished to obtain the metals in the 

 crystalline form. 



If, according to Pauli J, pentasulphide of phosphorus intimately 

 mixed with an excess of sal-ammoniac be heated in a retort over 

 the gas-lamj), hydrochloric and hydrosulphuric acids are disen- 

 gaged, togetlier with sal-ammoniac, and after some time yellow 

 sulphide of ammonium distils over. When the evolution of gas 



* Comptes Rendus, March 30, 1857. f Phil. Mag. vol. xiii. p. 124. 



X Liebig's Annalen, January 1857. 



Phil. Mag. B. 4. Vol. 15. No. 98. feh. 1858. I 



