16,6 Quisumhing: Determination of Glucose and Starch 583 
in alkaline solutions of all the common sugars undergoes steady 
acceleration from the beginning of the reaction and for some time 
thereafter. When air is the source of oxygen, the optimum 
concentration of alkali for oxidation is between N and 2 N, the 
velocity falling off in either direction. 
According to investigations made on the oxidation of sugars 
with alkaline potassium permanganate solution, smaller con- 
centrations of alkali are more effective than those used in the 
oxidation with air. Witzemann(i4) found that the optimum 
concentration of alkali lies close to 0.1 to 0.2 N, or between these 
two figures. He also observed that oxidation is markedly in- 
duced even by very small concentrations of alkali, 0.014 N alkali 
giving strong effect. 
EARLY INVESTIGATIONS OF THE METHOD OF ANALYSIS 
One of the earliest investigations on the oxidation of organic 
substances by pota&cium permanganate was performed by Ber- 
thelot. (1) He worked principally on the oxidation of fats and 
found that oxidation is greater in an alkaline than in an acid 
medium. Donath and Ditz(3) found that, when boiled at a high 
temperature and with relatively high concentration of potassium 
periranganate, organic bodies give carbon dioxide and water 
as oxidation products. Smolka, (13) experimenting on simple 
sugars, found that, when glucose is completely oxidized, the 
products of oxidation are carbon dioxide and water; and that, 
when oxidation is carried on in the cold, small amounts of oxalic 
acid are detected. Karez(6) performed a series of experiments 
on the oxidation of carbohydrates, using sugar solutions. The 
sugars were oxidized by heating the solution for fifteen minutes, 
with potassium permanganate containing 20 per cent of sulphuric 
acid, and determining the amount of oxalic acid produced by 
titration with standard potassium permanganate solution. Het- 
per(5) found that there is a difference both in the products and 
in the degree of oxidation, when this is carried on in acid or 
alkaline media. Donath and Ditz,(3) working on the same 
subject, came to the conclusion that oxalic acid is a product 
obtained when sugars are oxidized by potassium permanganate 
in an alkaline solution, while carbon dioxide and water are 
obtained in an acid medium. This conclusion agrees with that 
from Witzemann’s results. 
A series of oxidation experiments with carbohydrates was 
conducted by Greifenhagen, Konig and Scholl, (4) whose method 
of procedure is as follows: A definite number of cubic centi- 
