Intelligence and Miscellaneous Articles. 269 



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The following process yields a pure and perfectly crystallized oxide 

 of chromium : — heat neutral chromate of potash to redness in a por- 

 celain tube, and pass a current of chlorine over it ; the chlorine is en- 

 tirely absorbed, oxygen is disengaged, and there remains in the tube 

 a mixture of oxide of chromium in fine crystals, and chloride of po- 

 tassium : this crystallization of oxide of chromium appears to have 

 sonje analogy with that of peroxide of iron in the calcination of a 

 mixture of common salt and sulphate of iron. 



The temperature at which the reaction is effected influences the 

 crystallization of the oxide ; when the operation is conducted at a 

 low temperature, the oxide is in large transparent laminae of a green 

 colour ; but when the chlorine is passed over the chromate previously 

 made very hot, the oxide of chromium produced is then black and 

 very hard, and resembles that prepared by M. Wohler's process, 

 which consists in decomposing by heat the bichromate of perchloride 

 of chromium. — Ann. de Ch. et de Phys., December 1844. 



PERCHLORIDE OF CHROMIUM. BY M. WOHLER. 



By the following process a chloride of chromium is obtained which 

 contains more chlorine than the protochloride : — put into a porcelain 

 tube some peach-blossom coloured crystallized anhydrous chloride of 

 chromium ; heat it and pass over it a current of chlorine ; it is rea- 

 dily converted into a brown substance, which sublimes and has all 

 the properties of a perchloride. 



This perchloride differs, in the first place, from the protochloride 

 by its colour ; secondly, the anhydrous protochloride is well known 

 to be insoluble in water, whereas the perchloride is soluble and even 

 deliquescent ; when treated with hot water it is immediately decom- 

 posed, and yielding chlorine is converted into protochloride. The 

 author has not yet obtained this compound quite free from proto- 

 chloride, and has not, therefore, yet submitted it to analysis. — Ann. 

 de Ch, et de Phys., December 1844. 



DOUBLE CHLORIDE OF POTASSIUM ANf) CHROMIUM. 



M. Fremy remarks, that it is well known that chloride of chro- 

 mium does not combine directly with the alkaline chlorides ; but he 

 found that when these two chlorides were formed together, they com- 

 bined and formed double chlorides ; thus when chlorine is passed over 

 a mixture of charcoal and chromate of potash, a fine double chloride 

 of potassium and chromium is formed ; this is effected by putting the 

 mixture into a tubulated earthen retort, and when red-hot passing a 

 current of chlorine over it ; a considerable quantity of anhydrous 

 protochloride is formed, which sublimes, and at the bottom of the 

 retort there is found the double chloride of potassium and chromium. 

 This salt has a fine rose colour ; it is very soluble in water and de- 

 liquescent ; the water, which at first dissolves it, afterwards decom- 

 poses it into chloride of chromium and chloride of potassium. This 

 action shows that it is not possible to preserve'this salt in the humid 

 way ; it was found impossible directly to combine, by the agency of 



