CHEMICAL SCIENCE. 231 



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chloride of chromium to obtain metallic chromium. In this state the 

 chrome is chemically pure ; it presents the appearance of iron, but it is 

 less alterable by humid air. Heated in the air, it is converted into sesqui- 

 oxide. It resists nitric acid even when boiling. The density of galvanic , 

 chromium coincides with the density deduced from the atomic volumes, 

 and does not diifer much from the known density. These facts regard 

 only the metal prepared with one of the modifications of chloride of 

 chromium ; they leave completely undecided the question as to whether 

 the chromium of the green chloride is identical with that of the blue. 

 Professor Buasen intends to study this point. On diminishing the current, 

 the metal ceases to be deposited, and in its place appears a black powder, 

 not crystalline, anhydrous, formed of protoxide and sesquioxide of chro- 

 mium. Professor Bunsen obtained sheets of chromium of more than 

 50 square millimetres' surface; these sheets were friable, and presented a 

 perfect polish on the side which had been in contact with the platinum. 

 Manganiura was obtained in the same manner. The learned chemist of 

 Heidelberg thus prepared very friable plates of more than a 100 square 

 millimetres' surface ; these plates were oxidized in humid air almost as 

 readily as potassium. 



To reduce barium and calcium, a greater density of current is required. 

 These metals are taken in the state of chloride, reduced to concentrated 

 solution, and acidulated with hydrochloric acid. The boiling liquid is 

 poured into the polished porcelain capsule, and an amalgameter platinum 

 wire, communicating with the battery, is introduced. Calcium is deposited 

 on the platinum wire as a gray layer, which is easily detached, and contains 

 a little mercury. In presence of water or humid air, this amalgam of 

 calcium oxidizes rapidly with disengagement of hydrogen ; it burns with 

 brilliancy when heated. 



The precipitation of the calcium is effected only with difficulty ; in 

 consequence of its oxidizability, this metal is converted into lime, which 

 covers the electrode, and intercepts the current. To obtain an appreciable 

 quantity of this product, we can do nothing better than frequently remove 

 the quite dry gray layer, and amalgamate again the platinum wire before 

 returning it into the chloride. 



Barium is more easily extracted; chloride of barium, in powder, is 

 reduced into a paste by means of water acidulated with hydrochloric acid; 

 it is heated to 212 in a water bath, and the current is established. The 

 amalgam of barium which is thus produced is solid, of a silvery white, 

 and very crystalline. Exposed to humid air, it becomes heated, and is 

 converted into hydrate of baryta. Placed in a charcoal boat, and heated 

 in a current of hydrogen, it abandons the mercury, and the residue is 

 composed of porous barium, presenting here and there brilliant metallic 

 particles. Poygcndorjfs Annalen, 



