THE COLLOID-CHEMISTRY OF SOAPS 157 



" surface activity " of various chemical substances in permitting 

 the " wetting " of contiguous phases, etc., as drawn upon by 



Various authors (S. PLATEAU, 1 G. QUINCKE, 2 F. G. DONNAN, 3 



H. W. HiLLYER, 4 WALTHER OSTWALD, S T. B. ROBERTSON, 6 S. U. 

 PICKERING/ UBBELOHDE and GOLDSCHMIDT ? S WILDER D. BAN- 

 CROFT, 9 G. H. A. CLOWES, 10 S. A. SHORTER 11 and JAMES W. 

 McBAiN 12 ) to explain the nature of foaming and emulsification. 

 When water is changed to a liquid colloid hydrate, the properties 

 of the second are still the properties of a liquid, though quantita- 

 tively different from the first, and these properties include surface 

 tension, viscosity, distribution of dissolved and suspended parti- 

 cles, etc. But were we to express a critical opinion of the theories 

 of foaming and emulsification as developed by these various 

 authors, we would say that each has failed in the opinion of some 

 other author because he has used his theory as an exclusive one 

 and as one necessarily universally applicable. As we have repeat- 

 edly emphasized, a number of factors undoubtedly play a role, 

 and the relative importance of each varies not only in different 

 foams and in different emulsions but in one and the same foam 

 or emulsion under different circumstances. 



4. The Washing Properties of Soaps 



Empiric practice seems to have succeeded in furnishing soaps 

 of good washing properties for almost all technologic needs and 

 for use under the most varied circumstances, and this in spite 

 of the fact that we seem still to be largely ignorant of why in 



>S. PLATEAU: Ann. dcr. Phys.k . 111. 44 (1870). 

 G. QUINCKE: Ann. <l< -r Physik., 271, 580 (1888). 

 F. G. DONNAN: Zeitechr. f. pl.ys.k Chm. . 31. V2 1H99). 

 1 II \\ Hiu/kKK: Jour. Am. Chem. Soc., 26, 511 (1903); ibid., 25, 524 

 (1908] 



\\ M.iMKROKTWAi.n: K..ll..i,|./rit<rhr.. 1 <c ; (1910); ibid., 7,64(1910). 

 T. B. ROBERTSON: Koll,>i<l-/nisrl,r., 7, 7 (101' 

 '8. U. PL KI.IMN.,: K..lloi.l-/,'itsrl,r . 7. 1 



' UBBELOHDE and GOLDSCHMH-I ll:m<ll>tirh tier < )! und Fette, 8, 11, 

 L.IP/IU l'ln ; Znt.xrhr f Kl.'ktrorlii-m., 18, 380 (1912); Kolloid-Zoitachr., 



Koll.M.lrhrm Beihcftc, 6, 427 (1914). 

 Wu.i.MiD RAMCBOfTi JdW PhvM,-:,l Clinn . IT. W (1913). 



II A.CLOWEH: .lour Physical Clinn . 20. U'. 1910). 

 " S I- ..i r Hoc. Dyers and Coloristo, S2, 99 (1916). 



JAMES W. McBAiN and C. 8. S ur Am Chem. Soc., 42, 426 



IWO) 



