DOES HYDROGEN PEROXIDE OCCUR IN PLANTS, 
227 
uninjured, and the cuticula had prevented the entrance of 
the acid solution into the cells. In order to see whether the 
« 
reaction obtained was, indeed, due to hydrogen peroxide, I 
added 0.5 gr. of platinum black to 20 cc. of the diluted oxalic 
acid solution that had been in contact with the leaves for twenty- 
four hours, and let the mixture stand with occasional stirring in 
a porcelain dish for one hour. A control experiment with a 
0.1 % solution of hydrogen peroxide, having shown that by this 
means hydrogen peroxideS r) is so perfectly decomposed, that 
BacJds reaction shows not a trace of it, it was remarkable to find 
that in all the plants mentioned the reddish coloration was obtained , 
and still of the same intensity as before treatment with platinum black. 
The only conclusion to be drawn is that there was no hydrogen 
peroxide ever present, and it seems to me that Bach was not 
justified in declaring that it was so in any of the plants he ex¬ 
amined, because he omitted to apply the platinum test to see 
whether the faculty of giving this reaction would be destroyed 
or not. 
The coloration mentioned can very probably be obtained 
only in those cases where the leaves have been partially killed 
by the oxalic acid solution, and thus certain easily oxidisable 
organic matters made able to leave the cells by osmosis. These 
might by oxidation in presence of the aniline oxalate yield 
coloured products. 
I doubt whether Bach ever observed his reaction in leaves 
that had remained alive in all parts. 
(1) The energetic decomposition of hydrogen peroxide by platinum black is an 
old and well known fact. 
