DISOXIDATION EFPECTED BY THE ALEA.LINE PEEOXIDES. 
841 
oxide of hydrogen to the amount of oxygen evolved from the permanganate, then 
x~ 
ms 
Two distinct series of experiments gave the following results > 
I. 
5, =14-127, 
mi= 4-9025; 
whence 
5, =14-8, 
m, =11-919; 
s =14-1145, 
m= 4-91, 
^=1-0007. 
IL s =35-945, 
771= 4-91, 
whence ir= 0-9945. 
This experiment affords a simple and accurate method of determining by titration 
•with a solution of permanganate the absolute amount of oxygen in a solution of the 
peroxide of hydrogen. 
If e be the amount of oxygen contained in 1 cub. centim. of the permanganate, and 
y the amount of oxygen in 1 cub. centim. of the peroxide, then 
m-, 
7/= — e. 
"J m 
In the former of the above experiments 1 cub. centim. of the iodine solution contained 
0-00243 grm. of iodine, which are equivalent to 0-00017905 grm. of oxygen. 
Hence 
The oxygen in 1 cub. centim. of permanganate, as determined with iodine, 
= 0-000517 grm. ; 
The oxygen in 1 cub. centim. of peroxide of hydrogen, as determined with 
iodine, =0*0005147 grm. ; 
and 
The oxygen in 1 cub. centim. of peroxide of hydrogen, as determined with per- 
manganate, =0-0005144 grm. 
The above experiments prove that in this decomposition the decomposing substances- 
evolve equal quantities of oxygen*; the final result of the change may be thus stated, 
4HC1 + H2Mn4 Og + 5 H 2 02=4Mn Cl -f 8 H 2 O + 5 O 2 . 
I have varied this experiment in many ways, by adding the peroxide of hydrogen to the 
permanganate, and by taking the solutions excessively dilute and excessively concentrated, 
•with the view of eliciting a variation in the reaction, but have constantly obtained one and 
the same result. Although the above equation expresses accurately the final result of 
the decomposition, we are not to believe that the five molecules of oxygen are at once 
eliminated, but rather that the substance passes through five successive stages of disoxi- 
dation, very rapidly succeeding one another. If to an excess of an alkaline solution of 
permanganate an alkaline solution of the peroxide of sodium be added, oxygen is evolved, 
the solution still remains clear, but becomes of the characteristic green colour of the 
* This reaction has also been investigated by AscHorr with the same result. — Eepertoire de Chimie 
pure, vol. hi. p. 296. 
