CHEMICAL SCIENCE. 281 



on the contrary, it turns the edge of the best tempered files. It is capa- 

 ble of the very best polish. At the ordinary temperature it is unalterable 

 in moist or dry air : polished plates have been kept during two months 

 in the atmosphere of the laboratory, charged throughout with moisture 

 and other vapors, without the polish having suffered. Heated upon a 

 slip of platinum it approaches closely in color to steel, passing afterwards 

 into a brown, by covering itself with a coating of oxide. 



Its specific gravity has varied in different trials from 7'138 to 7'20G. It 

 is not attracted by the magnet, and even when in a state of powder, exerts 

 no influence upon the magnetic needle. Acids attack it rapidly. It dis- 

 solves easily in dilute sulphuric acid at the ordinary temperature. Nitric 

 acid dissolves it rapidly, so does hydrochloric acid, even when much diluted 

 with water, and likewise acetic acid. 



There cannot be a doubt that manganese, prepared in this manner, will 

 find applications in manufactures. The great hardness of this metal fits 

 it for mechanical use. Set at a sharp angle, it can advantageously be sub- 

 stituted for the diamond in cutting glass, and even in the polishing steel 

 and other metals. It is so susceptible of polish as to appear applicable 

 for the purposes of optical instruments ; for instance, the mirrors of teles- 

 copes. Although it cannot be forged, it can be rolled into shapes as easily 

 as the cast iron. In fine, the alloys of this metal are capable of yielding 

 useful substances ; and the attention of manufacturers arc now called to this 

 subject. It is an established fact, that all steel contains small quantities of 

 manganese. It has also for a long time been considered indispensable to 

 add substances which contain this metal to the powder used for the pur- 

 poses of cementation employed in making steel. The valuable variety of 

 steel, known under the name of Wootz, owes, perhaps, its properties to the 

 addition of manganese. 



CRYSTALLIZED CHROMIUM AXD ITS ALLOYS. 



BY M. FEEMY. 



The result of my researches was to examine, comparatively, iron, man- 

 ganese, and chromium, which form, as chemists arc aware, a true chemical 

 family amongst themselves, and to determine the influences which can, ac- 

 cording to their mode of preparation, vary the properties of these metals 

 and that of their alloys. 



/ 



I have ascertained, in the beginning, that manganese and chromium are 

 obtained in an absolute state of purity when the anhydrous chlorides of 

 these metals are submitted to the vapor of sodium. The decomposition 

 is effected in porcelain tubes, which are heated to redness, and the vapor 

 of sodiurn, introduced by means of a current of hydrogen, re-acts upon the 

 chlorides of the metals, which are placed in little nests or crucibles. Under 

 the influence of the alkaline chlorides that arc formed in the reaction, as 

 well as by the agency of the current of gas, the reduced metals assume 

 regular crystalline forms. 



The chromium, which has particularly attracted my attention, presents 

 itself in crystals, which shine with a great lustre when they are free, by 



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