hcraM, 1917.] NAGAI—THE ACTION OF OXIDASE ON ANTHOCYANIN. 69 



decomposed, no colour is produced, but in those which still 

 retain undecomposed anthocyanin, a distinct colour is formed 

 and its intensity differs according to the amount of anthocyanin 

 remained. The colour of any mixture in the series of plant 

 juice, is now compared with that of the series of hydrogen 

 peroxide, and ascertain which mixture in two series matches 

 best. In this way the oxygen value of the plant juice can be 

 estimated from the known concentration of the hydrogen 

 peroxide. It must be stated, however, that when the plant 

 juice or the powder is used, the colour produced by oxidation 

 of the chromogen 1 contained in the anthoc\'anin extract, 

 obscures the determination of the end point. In most of the 

 cases where the extracts of floral and foliage leaves of different 

 plants were examined, an orange red to a brown colour" 

 was produced. 



Some of the data may now be given to illustrate the mode 

 of action of the oxidising solutions so far discussed. Three cc 

 of the reduced alcoholic solution of quercetin (1 : 1000) is mixed 

 with 1.5 cc of hydrogen peroxide and the rate of decolourization 

 is measured by Duboscq's colourimeter. The temperature of the 

 mixture is not so rigorously controlled as might be expected, 

 but being kept fairly constant at 15° C. The initial depth of the 

 colour is taken as 100, and the intensity of colour measused nL 

 different intervals of time and expressed in per cent is given in 

 the following table (compare Fig. 1). Assuming that the reac- 

 tion is a mono-molecular one,' the value cf k culculated by the 



la 

 formula, k = . log seems to give a fairly 



t a — x 



agreement. 



6' 



1 ( If. Palladin's respiration pigment 



2 No. 78 -- 103, 138 in Klinokaieb el Valettb's Codi d< Coulours. 



•'; The assumption i- a rather tentative one. W< mu I :i»:iii further experiments 



Ul'.i. :wv< |.liiiL' ii fully. 



