ON COLLOID CHEMISTRY AND ITS INDUSTRIAL APPLICATIONS. 15 
palmitate ions. The suggestion we made is that we have here 
a new type of aggregate or micelle, the mobility of which, owing 
to the reasons given in the paper cited, is comparable with that 
ofa true anion. Of course, further investigations are proceeding 
in this laboratory in order to bring this to the test of direct 
experiment. Incidentally, the above shows, further, that undis- 
sociated soap is present chiefly or entirely in colloidal form.’ 
As I see the matter, the sodium palmitate is hydrolysed and 
the hydroxyl ions are adsorbed to a great extent by the undis- 
sociated palmitate, and possibly by the insoluble palmitate acid 
also, though this seems less probable. The adsorbing substance 
thus becomes the anion, owing to the adsorbed hydroxyl. Because 
of electrometric measurements, McBain*’ considers that there is 
practically no hydrolysis. Electrometric measurements only 
show the concentration of hydroxy] ions in solution. I do not 
believe for a moment that an adsorbed hydrogen ion or hydroxyl 
ion behaves electrometrically like a free hydrogen or hydroxyl 
ion. An adsorbed chlorine ion, for instance, would not give a test 
with silver nitrate. Under these circumstances the electrometric 
measurements are satisfactory for showing the concentration of 
hydroxyl ions in the solution, but they aré utterly worthless for 
showing the degree of hydrolysis of sodium palmitate. For the 
same reason I am very sceptical as to any conclusion in regard to 
‘albumin solutions which is based on electrometric measure- 
ments.*® 
So-called irregular series *® have been observed when a suspen- 
sion of a positively-charged colloid is added to a suspension of a 
negatively-charged colloid. When increasing concentrations of 
aluminium sulphate were added to a negatively-charged solution 
of mastic there was at first no precipitation, and the suspension 
was charged positively because the mastic was present in excess. 
At higher concentrations of aluminum sulphate, the suspension 
became electrically neutral, and complete precipitation took 
place. At still higher concentrations the mastic was held in 
‘suspension by the hydrolysed alumina, and the suspension was 
‘charged positively. At still higher concentrations of aluminum 
sulphate complete precipitation occurred. This apparently 
abnormal result is due to the fact that the experiment ‘is not 
exactly what it purports to be—the addition of one colloidal solu- 
tion to another. Instead of adding a colloidal solution of 
alumina, there was added a so-called solution of aluminum 
sulphate, which hydrolysed to colloidal alumina and sulphuric 
acid, with possibly some aluminum sulphate left unchanged 
especially in the higher concentrations. . The amount of free 
sulphuric acid is always equivalent to the amount of alumina, 
and the two concentrations increase proportionally. The so- 
called abnormal precipitation at the higher concentrations is 
merely a precipitation by sulphate ions, and is absolutely normal. 
-§7 McBain and Martin, Jowr. Chem. Soc. 105, 957 (1914). 
88 Bancroft, Jour. Phys. Chem. 19, 349 (1915). nadie) 
89 Neisser and Friedmann, Zit. angew. Chem. 1906, 1953; Bechhold, Zeit. 
Phys. Chem. 48, 285 (1904); Buxton and Teague, Zeit Phys. Chem 5'7, 47, 64 
(1907) ; Freundlich, Kapillarchemie, 402 (1909). 
