842 
PEOrESSOE B. C. BEODIE ON THE OXIDATION AND 
manganate of potassium. On the addition of a further portion of the alkaline peroxide, 
oxygen is again evolved, the solution becomes colourless, and hydrated peroxide of 
manganese is precipitated. If this precipitate be added to an acid solution of the 
peroxide of hydrogen, oxygen is again evolved, both the peroxides are destroyed, and a 
solution is formed of a protosalt of manganese, showing the successive formation and 
reduction of each of the oxides before the final result is attained. 
2. Becomjposition of a Solution of Peroxide of Hydrogen hy Ferricyanide of Potas&ium. 
When an acid solution of the peroxide of hydrogen is mixed with an acid solution of 
ferrocyanide of potassium, an oxidation takes place, and the ferrocyanide passes into 
ferricyanide of potassium. This action requires time, and takes place with extreme 
slowness in dilute solutions. 
If, on the other hand, an alkaline peroxide be mixed with an alkaline or neuti’al 
solution of ferricyanide of potassium, the reverse action takes place, oxygen gas is 
evolved, and the ferricyanide passes into the ferrocyanide of potassium. 
The proportion in which the substances are decomposed in this reaction was thus 
determined. 
A solution was made of ferricyanide of potassium, of which the value in terms of a 
standard solution of permanganate of potassium was ascertained as follows. A measured 
amount of the solution was converted to ferrocyanide by adding to it a great excess of 
recently precipitated hydrated peroxide of barium, the solution was boiled untd the 
excess of peroxide of barium was completely decomposed, and the amount of ferrocyanide 
formed was determined by means of the standard solution of permanganate *. 
A measured amount of a solution of peroxide of hydrogen, the value of which had 
been estimated by the process before described in terms of the same solution of per- 
manganate, was precipitated by an excess of baryta water. To this a measured amount 
of the solution of ferricyanide was gradually added by means of a pipette. After the 
experiment, the solution was diluted with water and acidulated. The excess of per- 
oxide and the ferrocyanide present was determined by means of the same solution of 
permanganate. 
It is evident that the subsequent addition of permanganate would efiect two results, — 
the decomposition of the excess of peroxide, and the reconversion of the ferrocyanide 
formed to the condition of ferricyanide. 
Since in an acid solution the ferrocyanide is oxidized by the peroxide of hydrogen to 
ferricyanide, a portion of the ferrocyanide reduced will have undergone that conversion, 
and an equivalent portion of the peroxide of hydrogen will have disappeared. 
Now, putting s=the parts of permanganate solution equivalent to 1 part of the solu- 
tion of peroxide of hydrogen employed, and 5i=the parts of permanganate solution 
equivalent to 1 part of the solution of ferricyanide employed, 
* This affords an excellent method for the estimation of ferricyanide of potassium. 
