ether, solvents in which the concentration of a fully saturated solution 

 would be very great. The fact that such extracts are far from 

 saturation — concentration is further proof that the fatty acid in the 

 aqueous layer cannot have reached its minute saturation value either. 



IV. — Evidence for, and Properties of, the Ionic Micelle. 



(a) Conductivity. 



Soaps particularly in concentrated solutions all exhibit a high 

 conductivity quite comparable with that of, say, sodium acetate. 

 This conductivity must be a property of the soap, since as we have 

 seen, there is very little free alkaU present, and there is nothing else 

 to which the conductivity can be ascribed. These points are well 

 brought out in the foUowmg table from McBarn and Martin's paper, 

 wliich comprises the conductivity of sodium and potassium palmitate 

 solutions divided in each case into their two components ; that due 

 to free hydroxide as indicated above and the remainder of the observed 

 conductivity which has to be ascribed to the soap itself. The ratios 

 of the conductivity of the soap to that of the corresponding acetate 

 solutions are also given for comparison : — 



Cone. Sodium Palmitate. Potassium Palmitate. 



fx NaOH [x NaP. NaP/NaAc. [x KOH. /x KP. KP/KAc. 



1-0 N - MO 83-6 0-644 0-46 123-7 0-699 



0-75 N - 1-65 85-8 0-619 1-87 126-0 0-685 



0-5 N - 2-1 87-4 0-568 3-8 123-2 0-627 



0-3 N - 2-7 84-3 0-499 _ _ _ 



0-2 N - 3-0 79-4 0-444 3-8 107-2 0-492 



0-1 N - 7-0 75-5 0-387 7-5 99-5 0-421 



0-05 N -12-2 76-4 0-368 12-1 98-7 0-396 



0-02 N - — — — 33-5 99-7 0-380 



0-01 N -36-0 101-7 0-446 40-6 1310 0-435 



The form of the conductivity curve is remarkable, and is such 

 as has hitherto been observed only for certain anomalous non-aqueous 

 solutions. Both relatively and absolutely, the conductivity is at a 

 minimum between 0-05 N and 0-1 N solution. Thereafter, mstead 

 of decreasing steadily with increasing concentration, the conductivity 

 rises to a pronounced maximum in 0-75 N solution. The relative 

 conductivity as compared with the corresponding acetate, has nearly 

 doubled with this same increase of concentration. These unique 

 relationships clearly establish that when such soap solutions increase 

 in concentration, the palmitate ion is being replaced by some other, 

 much better conductor of electricity, namely, the ionic micelle already 

 referred to. 



The experimental evidence for the reliability of these results rests 

 upon a very painstaking study carried out duruig several j^ears by 

 McBain and Taylor,- in which all possible sources of error were 

 carefully studied and eliminated in the special case of sodium palmitate. 



