Book Description

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1919 edition. Excerpt: ...' See, for example, the recent work of B. Lofller, Drude's Ann. d. Phys., 23, 3 (1907) ing degree of dispersion of the solid. This rule, however, applies only to average degrees of dispersion, for decided deviations are found when dealing with substances in a state of colloid subdivision. It would be of interest to have available a series of measurements showing the dependence of the density of a dispersoid upon the degree of dispersion. Measurements of density changes in emulsoid systems are more numerous. By direct observation in a dilatometer, H. Quincke1 found that the system, dried egg albumin-water (100 grams albumin + 163.9 cc. water) showed a decrease in volume amounting to 4.175 cc. after thirty-six hours. In another instance (100 grams albumin + 144.77 cc. water) a contraction of 5.168 cc. took place. In the latter instance the contraction in volume amounts to more than 3.5 percent. The densities of dried and hydrated cartilage were observed to be as follows: the calculated values in the table are the arithmetic means. Dried Hydrated. Hydrated. (observed density) (calculated density). _ _ X. __ _ 1.407 1.0892 1.0826 1.368 1.1124 1.1090 Chr. Liidekingf among others has made similar investigations on gelatine gels, and H. Rodewalds on starch. The following table gives some of their findings. TABLE 5 Observed density 'Calculated density Difference 10 percent gelatine........... 1.069 l 1.0412 0.028 20 percent gelatine............ 1.135 1.203. 0.032 50 percent gelatine............ 1.242 O 1.206 0.036 If the volume of 1 cc. of water after contraction is calculated from these figures the following values are obtained: For 10 percent gelatine.............................. 0.96069 cc. For 25 percent...