78 SOAPS AND PROTEINS 



not only in the specific instance of the different soaps but in all 

 similar colloid-chemical systems as represented by the most varied 

 types of chemical reaction encountered in technological practice and 

 in living cells under physiological and pathological circumstances. 1 

 Incidentally they also bring proof for the theoretical views devel- 

 oped above, according to which the system, soap-dissolved-in 

 solvent is something totally different from the system, solvent- 

 dissolved-in-soap. 



1 



Our fundamental conclusion may be stated thus: When a 

 " neutral " soap has been produced through combination of the 

 necessary gram equivalents of pure fatty acid with standard alkali, 

 it is either add, neutral or alkaline to such an indicator as phenol- 

 phthalein, depending upon the concentration of the water in the 

 system. 



For purposes of illustration we may choose the behavior of a 

 rather concentrated solution of sodium oleate, as one made by 

 combining one mol of fatty acid with one liter of normal sodium 

 hydroxid solution (practically a molar or 30 percent " solution " 

 of the soap in water). Phenolphthalein added to such a concen- 

 trated sodium oleate/water system remains colorless, as shown 

 in the lower portions of the test tube of Fig. 50. As soon, how- 

 ever, as water is added to this colorless mixture it begins to turn 

 pink, and, with increasing dilution of the soap, becomes bright 

 red, as evidenced in the upper portion of the tube in Fig. 50. 



What has been said of sodium oleate is true in general of all 

 the soaps (excepting such very low members as the formates, 

 acetates, etc.) though for demonstration purposes the higher 

 fatty acid soaps with their lower solubility in water are better 

 than the soaps of the lowermost members in any fatty acid series. 

 An indicator (like phenolphthalein) added to a chemically neutral 

 sodium palmitate or sodium stearate/water system (either a solid 



1 It may be well to emphasize here that normal cells are essentially sys- 

 tems of water-dissolved-in-protein. Indicators are therefore trickiest when 

 applied to these systems. In disease the affected cells suffer changes which 

 often are in the direction of "true" solution, in other words, the cells tend to 

 develop into systems of the type, protoplasm-dissolved-in-water. Indicator 

 methods become more reliable as this happens but only for those portions of 

 the cell which are of this "true" solution type. See the later pages of this 

 volume. 



