EFFECT OF HYDROGEN ION CONCENTRATION UPON THE RATE OF DESTRUCTION OF VITAMIN B UPON HEATING

Abstract

In the work of earlier investigators, summarized elsewhere,' it has been shown that alkalinity accelerates the destruction of vitamin B upon heating, but we have seen no record of experiments in which this has been studied quantitatively with reference to the actual or thermodynamic concentration or "activity" of hydrogen or hydroxyl ions.In a previous series of experiments carried out in this laboratory2 quantitative investigation had shown a destruction of approximately 20 per cent of the vitamin B present in tomato juice when this was heated for 4 hours at 100' at its natural acidity of pH 4.28; with a steadily increasing rate of destruction at higher temperatures under otherwise constant conditions.The purpose of the experiments here described was to determine quantitatively the effect upon the rate of destruction of vitamin B when heated at 100" in the same medium but with definite changes of hydrogen ion concentration in the direction of decreasing acidity and increasing alkalinity, the natural reaction of pH 4.28 being shifted successively to pH 5.2, pH 7.9, pH 9.2, and pH 10.9.These changes in the reaction of the medium resulted in successive increases in the rate of destruction of the vitamin.The methods and results of the measurement of these effects are here presented in very condensed form.