Physiology and biochemistry in modern medicine . the essentialproperty upon which the above-mentioned phenomena depend is the sizeof the particle. Particles which can still be seen under the microscopeare called microns. They have been computed to have a dimension fx ( mm.) or more, and they form suspensions. Particles whichare invisible microscopically under the ordinary conditions- of illumina- 54 PHYSICOCHEMICAL BASIS OF PHYSIOLOGICAL PROCESSES tion, but are still visible when the ultramicroseopic illumination isused, are called submicrons. They have a dimension between /* an
Physiology and biochemistry in modern medicine . the essentialproperty upon which the above-mentioned phenomena depend is the sizeof the particle. Particles which can still be seen under the microscopeare called microns. They have been computed to have a dimension fx ( mm.) or more, and they form suspensions. Particles whichare invisible microscopically under the ordinary conditions- of illumina- 54 PHYSICOCHEMICAL BASIS OF PHYSIOLOGICAL PROCESSES tion, but are still visible when the ultramicroseopic illumination isused, are called submicrons. They have a dimension between /* and1 /x/x (,001 mm.),* and they constitute the colloids. Particles smallerthan 1 fi/x are called amicrons, this term being used to include the mol-ecules and ions present in molecular solutions. (The amicron of hydro-gen is, for example, computed to be to /x/x, and that of watervapor, fi/x.) This classification of dissolved substances accordingto the size of the particles and molecules shows the relationship of one y Fig. 14.—Diagram from \V. Ostwald showing the relative size of various particles and colloidaldispersoids compared with a red blood corpuscle and an anthrax bacillus. class of substances to others. An idea of the relative sizes of colloidalparticles and molecules in comparison with such familiar objects as ablood corpuscle and an anthrax bacillus is given in Fig. 14. The fluidin which the particle is suspended is called the dispersion medium, orexternal phase, and the particle itself the dispersoid, or internal is the enormous development of surface which determines the dif- *M. — mm., and fifi = ,001 mr COLLOIDS 55 ference in the properties of a colloidal solution from those of a suspen-sion of the same substance. Thus, the difference between a colloidalsolution of platinum (prepared by allowing an electric ace to form between platinum electrodes in water) and pieces of platinum in waterdepends on the fact that
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