158 SOAPS AND PROTEINS 



actual use the soaps act as they do. The following paragraphs 

 do not pretend to bring a definitive answer to the problem, but 

 in connection with the remarks of the preceding paragraphs it 

 has seemed to us that they may help toward a formulation and 

 solution of some of the general problems involved. 



The oldest, perhaps, of the theories of washing holds that 

 soap owes its cleansing virtues to the alkali which it liberates on 

 solution in water. This factor as an important item in the wash- 

 ing process has been much discredited. While it is not to be 

 denied that its importance was formerly overestimated, it is 

 perhaps too extreme to deny it all virtue. The fact that even 

 soft water alkalinized through the addition of sodium, potassium 

 or ammonium hydroxid, sodium carbonate or borax washes better 

 than the water alone would seem to make it impossible to deny 

 the virtue of this factor entirely. 



On the other hand, the alkali factor cannot be the main 

 feature which gives soap its washing properties, for the very 

 soaps which on hydrolysis yield the largest overplus of free alkali, 

 namely, the soaps of the highest fatty acids, may wash most 

 / poorly. On the other hand, soaps which by test and under the 

 circumstances of their use are strictly neutral may function as 

 / ideal cleansers. To explain the action of soap under such cir- 

 cumstances, its power to produce foams and to emulsify has been 

 called into account, and this property has been paralleled with 

 its cleansing virtues. If this conception is correct and there 

 is much to support the idea that it represents the major factor 

 in the general washing power of the soaps then the value of dif- 

 ferent common soaps as generally employed would, on the basis 

 of our previous remarks, be about as follows: 



To produce effective cleansing a certain minimum of mechanical 

 washing methods are absolutely necessary. The soiled materials 

 must be " soused " in the wash water, rubbed on a washboard 

 or dragged about in a machine. This constitutes in the washing 

 process the equivalent of the mechanical element so necessary for 

 the production of foams and emulsions. The " dirt " in the 

 clothes is emulsified in the hydrated soap of the wash water. 



The soap must now be looked at from the point of view of 

 favoring such emulsification and the stabilization of the emulsion 

 after production. Obviously, of much importance in this matter 

 will be (a) the concentration at which the soap is used, (b) the 



