The Oxidation of Cane Sugar. 235 



It will be seen that the reduction in Experiment 1 was only 

 equivalent to 1 part in 1000, an amount only just recognizable 

 by volumetric methods, whilst in Experiment 2, a comparatively 

 large reduction has been effected by the formation of an 

 appreciable, though small, amount of MnOo. 



The accompanying plate shews that the curve, representing 

 the amount of action, at first runs just above and parallel to 

 the theoretical line until after passing the 3% mark, when it 

 crosses the line and suddenly bends downwards. 



The amount of sugar contained in 25ccs. of an aqueous 

 solution may be easily estimated in this way, provided that 

 between 1% and 3% of a milligram-molecule is present, a small 

 correction being made for the secondary action. 



But outside these limits the process, in its present form, is not 

 susceptible of much accuracy. 



Three methods of overcoming the difficulty have presented 



themselves (a) by increasing the duration of each experiment to, 



sa,y, two hours. This was tried, but the results obtained were 



unsatisfactory, (d) it was suggested that perhaps the sucrose 



would not itself reduce the KMn04, but would only do so after 



inversion, as in the case of "Fehlings" solution, and that 



consequently, if this were so, previous inversion of the sugar 



solution should considerably increase the velocity of the reaction. 



This was also tested by experiment, but without any notable 



result, (c) by increasing the amount of acid to 5ccs. or lOccs. of 



N 



-^ H2SO4 and if not too tedious, working at a lower temperature 



in order to minimise the secondary action. 



It is my intention to pursue this method further, as there is 

 room for a process capable of more than approximately estimating 

 the sucrose in such dilute solutions (0-3 per cent.) as we are here 

 concerned with. 



As previously intimated, it should be possible to deduce a 

 formula which will fit the curves that have been obtained at 

 101°, 94° and 85°C. ; of course a correction must be made for 

 the influence of the secondary action and this, though small, is 

 difficult to exactly determine. 



