484 Intelligence and Miscellaneous Articles. 



a little water, or what is still better, in a weakly alkaline liquor, and 

 crystallized ; without this precaution, the salt which crystallizes is 

 partly decomposed, retains always a certain quantity of acid alumi- 

 nate, and when subjected to analysis it gives more alumina than is 

 indicated by theory. 



When water is expelled from aluminate of potash by heat, it ap- 

 pears to be partially decomposed, for when treated with water a part 

 of the salt is found to be insoluble. Other salts formed by metallic 

 acids undergo similar decomposition by heat, 



Aluminate of soda is formed in the same way as aluminate of pot- 

 ash, but crj'^stallizes less readily. Other aluminates are all insolu- 

 ble ; they are formed by double decomposition, and possess but little 

 interest. 



Iron and Ferric Acid. 



M. Fremy remarks, that protoxide of iron is soluble in ammonia, 

 and forms a combination which has not hitherto been examined ; but 

 this oxide does not combine with the fixed alkalies ; when a solution 

 of a protosalt of iron is precipitated by a concentrated solution of 

 potash, and the liquor is boiled, it disengages a considerable quan- 

 tity of hydrogen ; the protoxide of iron is then converted into black 

 oxide ; the experiments of MM. Liebig and Wohler have shown 

 the facility with which protoxide of iron decomposes water. 



Peroxide of iron does not appear to combine with the alkalies in 

 definite proportion. When a i)ersalt of iron is precipitated by excess 

 of potash, the hydrate of the peroxide always retains a certain quan- 

 tity of potash ; the proportion of alkali combined is variable, and 

 never occurs in simple relation to the oxide of iron. 



If however the two oxides of iron do not combine directly with 

 the alkalies, the author observes, that he has found by superoxidizing 

 the sesquioxide of iron that it was converted into a compound which 

 has all the properties of an acid, and to which he has given the name 

 of ferric acid. 



Thus then, iron, like manganese, chromium, tin, and several other 

 metals, forms at first energetic oxides, and by superoxidizement yields 

 a metallic acid. — Ann. de Ch. et de Phys., Novembre 1844. 



ON A NEW CHLORIDE AND OXIDE OF CHROMIUM. 

 BY M. EUG. PELIGOT. 



It is well known that when a current of chlorine is passed over a 

 mixture of oxide of chromium and charcoal, that a chloride is ob- 

 tained which sublimes in fine violet-coloured scales ; this compound 

 corresponds to the sesquioxide of chromium, Cr^ O^ ; its composition 

 M. Peligot states from recent experiments to be represented by Cr^ 

 CP. 



This is not however the only chloride formed in this operation ; 

 it is preceded by another chloride which appears to have escaped the 

 notice of chemists, and which is in very white silky crystals, usually 

 mixed with charcoal and oxide of chromium ; these crystals become 

 green immediately on exposure to the air, and quickly become a green 

 solution ; they absorb both oxygen and moisture at the same time 



