282 ANNUAL OF SCIENTIFIC DISCOVEKY. 



washing them from the alkaline chloride with which they are found mixed. 

 These crystals have bccu examined and recognized as belonging to the cubic 

 systems. 



Chrystals of chromium are so hard, and have the curious property of re- 

 sisting the action of the strongest acids, and even that of nitrohydrochloric 

 acid. It is remarkable to observe chromium, which resembles in every 

 other respect mangnnese and iron, behaving itself like rhodium and indium 

 iu the presence of concentrated acids. These facts meet those of M. Dc- 

 viilc, recently established in his researches upon aluminum, demonstrat- 

 ing that amongst some of the elements we fail to establish a natural classi- 

 fication. 



It appeared interesting to study the alloys which chromium can form 

 with other metals, and it has been observed that these alloys present often 

 the hardness of the chromium, and resist, like it, the action of concentrated 

 acids. I have obtained the alloy of chromium and of iron, either by reduc- 

 ing by carbon the chromate of iron, or in heating in the fire of a forge iron 

 and oxide of chromium pure. This alloy crystallizes in long needles, 

 which are very hard, and scratch substances the most hard, even tempered 

 steel. 



In examining into the conditions which are most convenient in prepar- 

 ing the alloys of chromium, I have observed that the green scsqui-oxide 

 of chromium can be easily fused by the heat of a forge, and is changed into 

 a black crvstalline mass, which has all the characters of the crvstallized 



* * 



sesqui-oxide of chromium, obtained by decomposing chloro-chromic acid 

 by heat. This oxide can be obtained in considerable masses ; it scratches 

 quartz easily, as well as tempered steel. It, as well as the alloys of chrom- 

 ium, ought to have some application in the arts. 



TUNGSTEN AND ITS COMPOUNDS. 



The following paper by M. Riche, is derived from the Annalen des 

 Chemic, v. i. p. 5. 



Many processes have been proposed for the preparation of the metal 

 tungsten, but the process which ought to be employed is the reduction of 

 tungstic acid by hydrogen gas. 



If dry hydrogen gas be passed through a porcelain tube containing tung- 

 stic acid, heated to redness for at least two hours, a substance is obtained 

 which contains no oxygen, and which is the metal in a high state of purity, 

 provided the tungstic acid had been carefully prepared. 



It is an error to suppose that a higher temperature than what glass can 

 support is not required ; on the contrary, it ought to be very high, without 

 which the tungsten contains always a certain quantity of the lower oxide, 

 and does not present itself with the gray tint and crystalline appearance 

 which always characterizes it when in a state of purity. 



A modification of this process has been recommended, which consists 

 in substituting bitungstate of potash for the tungstic acid. The reduction 

 is more easy; however, for several reasons, it is not so valuable us the 

 former process. 



