1913.] A Study on the Action of Surface Tension. 533 



is confined to a deposit within the range of attraction of the molecules on 

 the interfacial surface. It is not improbahle that there is no sharp break 

 between the concentration at the interfacial surface and that in the solution 

 generally — that, in effect, there is a shading off between the two. The 

 amount adsorbed does, indeed, depend on the surface tension of the solution 

 at the interfacial line, and the effects of this surface tension do not extend 

 beyond the range of molecular attraction of the molecules on the interfacial 

 line, but in the case of the solutes which are adsorbed in such extraordinary 

 excess as to suggest the formation of a colloidal or gelatinous deposit, the 

 latter must tend to produce successively superposed interfacial deposits 

 until equilibrium is attained, in which case the deposit may extend with 

 lessening concentration through a distance from the interfacial surface 

 equivalent, it may be, to several, if not many, times the range of molecular 

 attraction. 



These facts make it evident that in solutions in which interfacial surfaces, 

 numerous as in emulsions and consequently of very great areal value, 

 exist, the concentration of the solutes may fall very considerably through 

 condensation of the solutes on the interfacial surfaces. This must result in 

 lowering the osmotic pressure. The dissolved molecules free in the solution 

 are fewer, and their pressure is less than that of the molecules in the simple 

 homogeneous solution unaffected by surface tension, except at its boundaries 

 or limiting surfaces. The osmotic pressure of a solution of potassium 

 chloride contained in a beaker is, therefore, different in value from that of 

 the same solution and like concentration in which numerous interfacial 

 areas obtain through the presence of very numerous foreign non-soluble 

 systems. 



The elemental unit of living matter, the cell, is constituted of unhomo- 

 geneous material in which the essential constituents are chiefly in colloidal 

 condition, that is, the constituents are minute particles or dispersoids, 

 separating which is a fluid containing in solution the salts and other 

 compounds characteristic of living matter. Such dispersoids present inter- 

 facial surfaces of very great areal value, and if the surface tension of the 

 fluid at the fluid-dispersoid interface is lowered by the solute or solutes 

 there must be condensation of them on these interfacial surfaces. This 

 would lower very considerably the concentration of the solutions in the 

 fluid diffused through the living matter, and thus the osmotic pressure, 

 otherwise due to the presence of such salts in living cells, would be nearly 

 correspondingly reduced. 



Surface tension, therefore, through the operation of the Gibbs-Thonison 

 principle determines in a very considerable degree the distribution of salts 



