260 Gooch and Austin — Oxidation of Manganese. 



Akt. XXXIII. — On the Condition of Oxidation of Manganese 

 precipitated by the Chlorate Pi'ocess ; by F. A. Gooch and 

 Martha Austin. 



[Contribution from the Kent Chemical Laboratory of Yale University— LXVIIL] 



Hanjsay,* who was the first to propose the precipitation of 

 manganese from its solution in nitric acid by the use of potas- 

 sium chlorate, states that precipitation is complete, but that the 

 oxide produced is not of constant composition. While, there- 

 fore, precipitation by this method serves an excellent purpose 

 in separating manganese from other substances, it was Han- 

 nay's opinion that reliance cannot be placed upon the determi- 

 nation of the oxygen value of the oxide to estimate the 

 manganese. Beilstein and Jawein,f who proposed the same 

 method, subsequently, regarded the precipitate as the oxide 

 Mn0 2 . Hannay's reaction was developed, independently, by 

 Hamper and Ford§ into the method which is now known as 

 the " chlorate process " for the estimation of manganese. The 

 discussion of the exact condition of the precipitated oxide was 

 very active ten years ago, and occasional echoes of it are heard 

 at the present day ; and yet, in all this discussion we find no 

 account of an adequate test of the process upon an exact 

 amount of a salt of manganese known to be pure. The dis- 

 cussion for the most part has centered about the degree of 

 oxidation of the precipitate, but there is obviously another 

 condition to be taken into account, viz : the possibility of the 

 mechanical inclusion of the comparatively insoluble chlorate 

 in the precipitated oxide. As to the existence of the latter 

 source of error we have had in the course of our work very 

 strong affirmative evidence, the apparent condition of oxida- 

 tion of the precipitate being sometimes so high as to be other- 

 wise inexplicable. This difficulty does not occur, however, 

 when a more soluble chlorate is chosen to do the work of oxi- 

 dation, and we have found quite as convenient and much safer 

 the substitution of sodium chlorate for the comparatively 

 insoluble potassium chlorate. Besides, the rapidity with which 

 the sodium chlorate is decomposed makes its use an advantage. 



With regard to the completeness of the precipitation our 

 experience has shown that with due precaution the method is 

 practically perfect. Thus, after boiling manganous nitrate 

 (free from chlorides and sulphates) with strong nitric acid 

 (85 cm3 ) and sodium chlorate (5 grms.) for five minutes, adding, 

 subsequently, 15 cm3 of the nitric acid and a few crystals more of 



* Jour. Chem. Soc, vol. xxxiii, 269. 

 fBer. d. d. Chem. Gesell., xii, 1528. 

 % Chem. Central-Blatt., 1885, 714. § Trans. Inst. Am. Min. Engineers, ix, 347. 



