278 ANNUAL OF SCIENTIFIC DISCOVERY. 



ON SOME GEXERAL METHODS OF PREPARING THE EARER 



ELEMENTS. 



M. Deville has lately published some interesting memoranda upon the 

 subject which is now attracting so much attention in France and Germany, 

 the preparation of the rarer metals. Devillc is of opinion that the best mode 

 of preparation consists in igniting the oxide with carbon, taking care to em- 

 ploy an excess of oxide. It is however an indispensable precaution to fuse 

 the metal in a crucible of lime or magnesia. Crucibles of clay, porcelain, c., 

 are like borax partially reduced by many metals and even by platinum. The 

 silicon produced considerably increases the hardness and fusibility of the 

 metal. In a crucible of lime the oxide of chromium or manganese in excess 

 is absorbed by the lime, forming a chromitc or manganite which fuses with 

 great difficulty, but which removes from the metal all traces of carbon and 

 silicon. The fusibility of the metal diminishes as its purity increases, and 

 the author found chromium less fusible than platinum. Deville remarks 

 that manganese, as prepared by Brunner's method, may still contain carbon. 

 Sodium prepared from the carbonate always contains more carbon, and 

 moreover, from its porosity it frequently retains naphtha, which leaves a 

 carbonaceous residue when heated. The employment of Hessian crucibles is 

 also objectionable, as silica is easily reduced by sodium, especially in the 

 presence of the fltiorids. In this manner the author explains the differences 

 between Brunner's manganese and that prepared by himself, which is less 

 fusible than iron, and decomposes water at ordinary temperatures. The em- 

 ployment of sodium, on the other hand, presents great advantages when we 

 wish to obtain an element in a crystallized state. In this case the sodium 

 may often be replaced by aluminum, as for example, in preparing silicon, 

 titanium, zirconium, and boron. In the case of the scsquichlorids of zirco- 

 nium, aluminum or chromium, it is always well to make the sodium react 

 upon the double chlorids which these bodies form with chlorid of sodium. The 

 process should be conducted in a crucible of alumina which is to be heated 

 to redness before putting in the mixture of chlorids. In the case of the fusi- 

 ble metals it is well to add to the whole a little double chlorid of sodium and 

 potassium. Deville and Damour are now applying this process to the 

 cerium metals. Sodium attacks porcelain at a low red heat with such en- 

 ergy that there is always danger of introducing silicon into metals reduced 



o / t/ 



in such vessels. This perhaps explains the difference between the properties 

 of chromium as prepared by Fre'my and that prepared by Deville and Bun- 

 sen, the latter being readily soluble in chlorhydric acid giving a blue solution 

 of the protochlorid. In conclusion, the author again recommends the em- 

 ployment of crucibles of lime which refine the metals fused in them. The 

 platinum metals fused in such crucibles present properties very different 

 from those usually attributed to them, the lime serving to deprive them of 

 osmium and silicon. Comptes Rendus, xliv, 673, March oQth, 1857. 



