Introduction to physiological chemistry / by Meyer Bodansky.

  • Bodansky, Meyer, 1896-1941.
Date:
1934
Catalogue details

Licence: In copyright

Credit: Introduction to physiological chemistry / by Meyer Bodansky. Source: Wellcome Collection.

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    is less tlian 2 per cent. Grollman has measured the lowering of the vapor pressure of colloidal solutions (gelatin, gum acacia) caused by adding NaCl, KCl, and other substances. His results show that the degree of hydration is relatively small in gelatin and undetectable in gum acacia. Consequently, the assumption that hydrophilic colloids are strongly hydrated or that part of the water is bound’’ is untenable. Sunderman investigated the osmotic pressure of the blood by the freezing-point method and found all the water to be ‘^free,” a con- clusion in harmony with Hill’s observations. Even more convincing are the data of Greenberg and Greenberg, who studied the problem by the ultrafiltration method. They added various substances (glucose, urea, NaCl, KCl) to colloidal solutions (casein, gelatin, starch, pectin, glycogen, blood serum). A crystalloidal substance, according to the theory, should dissolve only in the ‘Tree” water. If the solution is filtered through a membrane which permits only the passage of the solvent and other crystalloids, holding back the colloidal constituents, the concentration of the substance in the ultrafiltrate becomes a measure of the “free” water in the colloidal solution. It was found that the concentration of the substance in the colloidal solution (based on the amount of total water) was equivalent to the concentration in the filtrate. This seemed to justify the conclusion that at most only a very small fraction of the water can be associated with the colloid in “bound” form. In short, many of the available data fail to support the concept of “ free ” and bound ” water. Nevertheless, the subject cannot be dis- missed lightly as it will probably continue to receive considerable atten- tion, partly because of the nature of the problems that have been brought into the discussion. Aside from the physiological and pathological aspects of the subject, there are such problems as the relation of the state of water to the winter hardiness of wheat, the resistance of wheat to drought, the resistance of fruits and insects to cold—problems whose economic importance is self-evident.