ON COLLOID CHEMISTRY AND ITS INDUSTRIAL APPLICATIONS. 129 
chloroform be shaken with a solution of methylene blue in water, 
the chloroform phase is found to be coloured. blue. In order to 
understand what this really means, we must refer to the work of 
Loewe (1912). He shows that kephalin is not in true solution in 
chloroform, but in large colloidal aggregates, since no measurable 
change in the boiling point of chloroform is produced by dissolving 
kephalin in it. The second point brought out is that, when meth- 
lene blue is present in the two phases, water and lipoid-chloroform, 
in contact, if it were a case of true solution in the latter, there would 
be a definite ‘“ partition-coetficient,’ independent of the absolute 
concentration. This is not the case. There is relatively less in the 
latter phase as the concentration rises, and the law followed is 
the parabolic law of adsorption. The actual ratio is such as to 
involve a high polymerization of the dye in both solvents, 
whereas electrical conductivity measurements indicate normal mole- 
cular weights in water. Again, if the dye were dissolved in the 
lipoid, a notable proportion of it would escape to water if placed 
in contact with it. Only a very minute amount leaves the lipoid. 
In fact, it behaves just like a negatively charged surface such as 
that of paper in water, to ‘basic’? dyes, which are hydrolyzed in 
solution, and whose coloured base becomes a positively charged col- 
loidal particle. As Freundlich has pointed out, the adsorption in 
such cases is so great that equilibrium is only effected when a very 
small amount of the dye is left in the water. Further confirmation 
of the view that we have to deal with a surface condensation only is 
that, if a mass of kephalin be placed in contact with a solution of 
methylene blue in water, the dye does not pass into the lipoid. 
Similar evidence was obtained in the cases of other “ lipoid-soluble ” 
substances, such as the alkaloids and certain narcotics. lt is impos- 
sible to accept the view that the cell membrane is a lipoid film, and 
that the passage of substances into and out of the protoplasm depends 
on their solubility in lipoids. 
It is also easy to show that a membrane of pure protein, as held 
by some, has not the requisite properties. Nothing but a complex 
system of more than one phase will suffice to explain the changes 
in permeability which are shown by the surface membrane of the cell. 
We have already spoken of the effect of certain electrolytes on 
the membrane. Further discussion as to the meaning of “ balanced” 
action will be found in the following section of this report. A few 
more facts in connection with permeability may be given here. 
Newton Harvey (1914) was unable to find any general law as to the 
relation of cells to acids, except that if an acid is soluble in lipoids it 
penetrates freely ; if not, the cell surface must be changed before it 
can enter. Strong bases do not enter; weak bases do. ‘This fact 
suggests that the permeability is in respect of one ion unly. Since 
weak bases enter, OH’ ions must do so. Therefore, when sodium 
hydroxide does not, it must be that the sodium ion is obstructed. 
This point was indicated by Ostwald (1890). It is sufficient for a 
membrane to be impermeable to one of the oppositely charged ions 
of an electrolytically dissociated solute in order that the solute may 
be completely kept out. The reason is because the two ions cannot 
be separated without the expenditure of a large amount of energy 
20895 E 
