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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    their mass. Adsorption is thought to be a factor in the staining reactions of tissues, the action of drugs, and many other phenomena. Suspensoids and Emulsoids. The division of colloids into two classes is based on the ability of some colloids to take up water. Kaolin, platinum, gold, arsenious sulfide, etc., when in the colloidal state consist of pure solid and are hence classified as suspensoids (also lyophobic, or hydrophobic, literally ‘^water-hating,’’ colloids). Other colloids in aqueous solution have so marked an attraction for water that the dispersoid may contain large quantities of water. These are the emuU soids (also hydrophilic or lyophilic, literally “water-loving,” colloids). The latter group is of primary importance physiologically, protoplasm being essentially an emulsoid type of colloid. Other familiar examples are starch, soap, egg white, and gelatin. No confusion should arise due to the fact that colloidal systems in which both phases are liquid are usually classified as emulsions. The name emulsoid is properly confined to those cases in which the internal phase contains more or less water, although it may sometimes more closely approximate a solid. It would be impossible to give an acceptable classification of colloids without bringing into the discussion a considerable amount of detail and the conflicting points of view of several authorities. This information belongs more properly to works devoted to colloid chem- istry. 2 ^ Viscosity. Viscosity is due to the internal friction of the molecules of a liquid. Solutions are almost always more viscous than the pure solvents. The viscosity of suspensoids in water is not much greater than that of the water, but in the case of emulsoids the viscosity is very markedly increased. Thus, the viscosity of 1 per cent agar is several thousand times that of water. Increasing the concentration of the dis- persed phase, particularly in the case of emulsoids, increases the vis- cosity of colloidal systems. Size of Colloidal Particles. The limit of vision with the aid of the microscope is about 0.0001 mm. or 0.1Colloidal particles range in diameter between 1 m^u and 100 mg (1 g = 0.001 mm.; 1 mg = 0.001 g) and therefore are below the range of microscopic visibility. It is possible, however, to detect particles of colloidal dimension by their diffraction images. Faraday, and later Tyndall, observed that when a beam of light is sent through a clear solution of finely divided For a comprehensive survey of the theoretical aspects of colloid chemistry, as well as of its applications in biology and medicine, the student is referred to “Colloid Chemistry—Theoretical and Applied,” edited by J. Alexander, Chemical Catalog Co., New York, Vol. I (1926); Vol. II (1928); Vol. Ill (1930); Vol. IV (1932). /X = micron; m^u = millimicron.