OF ARTS AND SCIENCES. 339 



set of tools, and occupies considerable time. It is as a rule distasteful 

 to the student, and is rarely resorted to even by experienced analysts, 

 unless the color of the solution, a preliminary blowpipe test, or some 

 incidental observation, has already indicated the probable presence of 

 chromium in the substance under examination. 



It is obvious, that if the chromium in the mixed precipitate could be 

 oxidized in the wet way by some simple and rapid method, it would 

 not only be more readily detected in any case, but the chances of 

 overlooking it altogether — an event now so liable to occur — would be 

 materially lessened, 



Frommherz * long ago noticed that chromic acid is formed when an 

 aqueous solution of a salt of chromium is treated with a solution of 

 permanganate of potash, — a fact which has since been corroborated 

 by Reynoso,t and still more recently by Cloez and Guignet.j Rey- 

 noso has suggested, moreover, that this reaction may be employed for 

 the detection of chromium, especially if the chromic acid formed be 

 subsequently converted into Barreswil's perchromic acid. 



Chancel,§ on the other hand, has observed that chromic acid is 

 formed when sesquioxide of chromium is heated with solution of caustic 

 potash in presence of peroxide of lead ; as may be shown by acidify- 

 ing the filtrate from this mixture with acetic acid, chromate of lead 

 being precipitated. He has also proposed || that this reaction shall be 

 used as a test for the detection of chromiuni. 



After a number of experiments upon the subject, I have satisfied 

 myself that peroxide of lead is as good an agent as any at our disposal, 

 if it is not the best, for effecting the oxidation of sesquioxide of chro- 

 mium by the wet way, while the formation of perchromic acid is un- 

 questionably the most delicate and characteristic reaction for chromic 

 acid which we possess. This note, therefore, must be considered as 

 being merely supplementary to the statements of Chancel and Reynoso. 



Besides the observations of these chemists are those of Balard,^ 



* Schweigger's Journal f. Ch. u. Phys., 1824, XLI. 281. 

 t Ann. Ch. et Phys., 1851, (3), XXXIII. 324. 

 t Comptes Eendus, XL VII. 712. 

 § Comptes Eendus, XLIII. 928. 



II Loc. cit , and Precis d' Analyse Chimique Qualitative, par Gerhardt et Chancel, 

 (Paris, 1855,) pp. 112, 289. 

 1 Ann. Ch. et Phys. (2), LVII. 266. 



