Abstract
Because it seemed probable that variations in reaction had affected the results obtained when dilute aqueous solutions of carbohydrates were boiled, 1 the investigation was extended to include buffered solutions. Phosphate mixtures were chosen because we wished to study solutions at approximately neutral reactions. Since it seems possible that phosphate may have some specific effect upon the transformation of aldoses into ketoses 2 experiments with acetate buffer mixtures were also carried out. The effect of oxygen and nitrogen upon the reaction and the fermentability of the compounds in the boiled solutions were also investigated. The technique is described in the preceding paper.
In Table I are given the results of experiments in which the phosphate content of dilute glucose solutions was kept constant and the degree of acidity varied. It is evident that both the speed of formation of “fructose” and of decrease in the reducing power varied with the reaction: they were highest in the most alkaline and lowest in the slightly acid ones. It is worth noting that a measurable formation of “fructose” could be demonstrated when the reaction was 6.0 pH. The change at a pH of 7 resembled that found in simple aqueous solutions, for diminution in the reducing power was very slight during the first 2 hours of boiling and quite marked during the latter part of the experiment when ketose was already present in relatively high concentration. When the pH value was 7.8 a marked ketose formation accompanied the rapid destruction of sugar.
In Table II are presented the results obtained when mixtures of sodium acetate and acetic acid giving pH values over the range shown in Table I were used. The difference between the 2 sets of results was slight and probably not significant.
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