64 SOAPS AND PROTEINS 



ON THE GENERAL THEORY OF THE LYOPHILIC COLLOIDS 



1. Historical and Critical Remarks 



The experiments detailed above on soap/water, soap/alcohol 

 and soap/x systems help, we think, towards a better understand- 

 ing of a number of technological, physico-chemical and biological 

 problems. We wish first to comment upon their value for a 

 closer definition of the terms hydrophilic or lyophilic colloid. 1 In 

 spite of the fact that we now recognize the existence of material 

 in the colloid state and utilize its many important properties 

 for the solution of technological or scientific phenomena, it is 

 nevertheless true that an entirely satisfactory or complete defini- 

 tion of what constitutes the colloid state is not yet at hand. 



Perhaps the best established and most universal character- 

 ization of the colloids is that which defines them as diphasic or 

 polyphasic systems in which one material is subdivided into a 

 second with the degree of subdivision coarser than molecular 

 and not so coarse as to fall within the limits of microscopic visi- 

 bility. From the three states of matter, gaseous, liquid and 

 solid, it is obvious, as first clearly developed by WOLFGANG 

 OsTWALD, 2 that nine combinations consisting of the colloid dis- 

 persion of any one of these materials in any second are possible. 

 These may be tabulated as follows; 



gas in gas liquid in gas (steam) solid in gas (smoke) 



gas in liquid (charged 



water) 

 008 in solid (meerschaum) 



liquid in liquid (fine emul- solid in liquid (metallic gold in 



sion) water) 



liquid in solid (opal) solid in solid (gold ruby glass) 



Of the nine possible combinations eight have been realized (the 

 colloid dispersion of one gas in a second being impossible). 



1 MARTIN H. FISCHER and MARIAN O. HOOKER: Science, 48, 143 (1918); 

 ibid., 49, 615 (1919); Chem. Engineer, 27, 184 (1919). 



2 WOLFGANG OSTWALD: Kolloid-Zeitschr., 1, 291, 331 (1907); Theoretical 

 and Applied Colloid Chemistry, translated by MARTIN H. FISCHER, 42, New 

 York (1917); Handbook of Colloid Chemistry, 2nd English Ed., translated 

 by MARTIN H. FISCHER, 43, 49, Philadelphia (1918). 



