301 
greatly retard this oxidation, specially if this solution is alkaline, 
and the inhibitory effect of sucrose, invert sugar, asparatic acid, etc., 
have been noted by SairLanD (Zeit. Ver. Zuckerind. 1913, 68, 1035). 
In 1912, we conducted some experiments on this line. From prelim- 
inary experiments it was observed that the velocity of the reactions 
depends greatly on the quality of the water used. Ordinary distilled 
water was found quite inefficient as it contained sufficient dissolved 
salts and gases to affect the course of the reactions materially. 
Freshly prepared conductivity water obtained according to the method 
of Jones and Mackay (Zeit. Phys. Chem. 1897, 22, 237) was always 
used. The salts used were purified by reerystallisation from con- 
ductivity water and dissolved in the same water in resistance glass 
bottles. Well steamed Jena flasks were used as vessels in which the 
reaction took place. In short every care was taken to ensure purity. 
But in spite of all this care, it was found that velocity coefficients 
of the reactions carried out under identical conditions but on different 
days and even at different times on the same day were slightly 
different. Trrorr also found similar results. The explanation is 
probably that the reaction is so susceptible to external conditions, 
that even the slight variation of circumstances that is inevitable 
when we carry out the same reaction at two different times are sufficient 
to affect the results. It is therefore clear that our comparison of the 
results tried on different days or with different concentration of the 
same catalyst, cannot give an accurate idea of their relative effect. 
To remove this difficulty, at least partially, we carried out a blank 
experiment in which no catalyst was added, simultaneously with 
the main one. Two similar ERLENMEYER flasks of capacity 150 c.c. 
were arranged side by side. A detinite volume of sulphite was put 
in each flask. The catalyst was added in one flask. The course of 
the reaction was determined and their coefficients calculated. The 
ratio of these two coefficients gives the measure of the catalytic 
effect of the substance under consideration. In this way it was found 
that the ratio between the coefficients of two similar pair of reactions 
carried out on different days were almost the same, though their 
absolute velocities varied appreciably. The flasks were exposed to 
the atmosphere whose oxygen served as the oxidising agent. 
N 
About fan iodine and thio sulphate solutions were used as titration 
liquids. A definite volume of the sulphite solution is pipetted in a 
flask containing an excess of standard iodine and the excess of 
iodine was titrated back with the standard thio sulphate. 
The temperature of the experiments was about 30° C. 
20* 
