224 SOAPS AND PROTEINS 



by the concentrations of the various materials existing in any sys- 

 tem, by the content of water in the system and the temperature. 

 Every one of these systems may be produced at will from 

 fatty acids and alkali or from " neutral " proteins with alkali 

 or acid. 



2 



It will be noticed that the above remarks attempting to 

 explain the colloid-chemistry of protein/ water systems have 

 called for no concepts outside those of mutual solubility and 

 mutual emulsification or suspension, just as in the case of soap/ 

 water systems. . What then becomes of the chemical, electrical, 

 surface tension, adsorption, etc., theories of stability in colloid 

 systems proposed by various authors? The answer is, we think, 

 simple. Their views are not always wrong, but they suffer 

 universally from one-sidedness. They err either because they 

 are inadequate to explain more than a part of the behavior of 

 all colloid systems or because the explanation holds for only 

 limited examples. If reference is again made to Figs. 48 and 49 

 it will be seen that those authors, for example, who try to see 

 in all colloid systems nothing but special instances of modified 

 " true solutions " are clearly trying to find the explanation of 

 all colloid phenomena in regions lying above the level E, and 

 that often they are attempting to do this by the changes incident 

 to mere passage from some one horizontal level to the next. Such 

 a view is obviously too limited, for it ignores the behavior of all 

 such systems as lie below the level V. Those authors, on the 

 other hand, who hold that change in some one factor is responsible 

 for the changes in stability of all colloid systems suffer from a 

 similar limitation in point of view. It is difficult, for example, 

 to conjure up electrical notions to explain the stability of colloid 

 systems which consist merely of organic solvents and materials 

 like fat or rubber. Stoichiometrical relationships lose their force 

 when stabile colloid systems can be built of most variable pro- 

 portions of fat and a hydratable carbohydrate (for example 

 cottonseed oil in hydrated acacia, glycogen or dextrin). Sur- 

 face tension views are inadequate when, with progressive change 

 in surface tension relationship between any two substances, stabil- 

 ization is obtainable only through a portion of the range, or, con- 



