[基础科学]清酒化学分析三.pdfVIP

21 nite conclusions from single experiments, but the very large percentage dissolved when 100 grams of koji were digested with 10,000 c.c. of water, bears out the above observa- tions. We have next to consider the influence of time upon the nature of the soluble matter. We have seen that it does not after 3 or 4 hours at the ordinary temperature affect very much the total amount of solids dissolved. But column VIII, which gives the average spe- cific rotatory power of three series of experiments lasting respectively 18, 12, and 3 hours, shows that at 18 hours the specific rotatory power is smaller than at 12 hours, and at 12 hours less than at 3 hours. What is the meaning of this variation? The specific rotatory power of the solution is made up of three factors. The specific rotatory power of dextrin is 216˚, that of dextrose is 59˚. If these were the only two substances present the specific rotatory power of the solution would lie between these two numbers having a value pro- portionate to the amount of each present. It will be seen however, that the average of the experiments at 18 hours is less than 59˚, and this shows that something else is present which tends to lower the value of the specific rotatory power. The albumenoids which are held in solution have been ascertained by nitrogen determinations to have an average value of –40˚, and it is owing to their presence that the specific rotatory power is so low as it is. The composition of the liquid in experiment 6, for example, will illustrate this more clearly. 100 c.c. of the solution contained 1.695 gram dextrose, 0.723 gram dextrin, and 0.914 of albumenoids (calculated by multiplying the nitrogen found by 6.3). This gives a composition in 100 parts shown in the table below. Dextrose 50.9% Dextrin 21.7% Albumenoids 27.4