ON COLLOID CHEMISTRY AND ITS INDUSTRIAL APPLICATIONS. 71 
apparently abnormal phenomena. Later on van Bemmelen proved 
that the phenomena were precisely similar to those shown by 
colloids, and argued that the soil must be treated as a colloid. 
This view was generally accepted by those who read his papers. 
Unfortunately, van Bemellen’s work was published in German, 
and the translation from his own language was not altogether 
happy—rather giving the impression of a long drawn tedious 
memoir on an unimportant subject. A good English translation 
is very desirable: the papers belong to the classics of agricultural 
chemistry. Van Bemellen did not at once arrive at the colloid 
explanation; he first accepted Way’s chemical explanation, and, 
indeed, devised a method for estimating the double silicates 
present. Later on, however, he made extensive studies of 
absorption by simple gels, silica, alumina, ferric hydroxide, tin 
hydroxide, etc., and found it closely to resemble absorption by 
soils: other studies of colloids were made, and in each case the 
similarity to soil phenomena was so close as to leave no doubt that 
soil was essentially a colloid and soil absorption simply a mani- 
festation of its colloidal properties. 
This new idea was soon found to explain many of the old dis- 
erepancies. Chemists had several times attempted to bring 
the phenomena of absorption equilibrium into line with those of 
chemical equilibrium, but the equations would not fit except for 
a narrow range of concentrations. 
When, however, the adsorption formula is used, a much closer 
fit can be obtained: Wiegner has gone over the recorded data and 
shown that they all agree with the ordinary equation, 
1 
J = Ker 
m 
the constants having the following values :— 
Absorbent. | Solute. K v | Worker. 
p 
Garden soil ... sp .. | NH,Cl 0:0948 0039 |\ Henneberg and 
ee tas, |, NACL 0-131 0-424 If Stohmann. 
Nile sediment aa aoe NH,Cl 0°489 0:399 | Armsby. 
Permutite ... NH,Cl 2°823 0°398 Wiegner, 
Sodium veotie | artist { CaCl» 2°487 0°317 Armsby 
Zeolite LiCl 24°419 0-414 Campbell. 
Soil ... eas “eo .. | NH,OH 0-0994 0°434 
eee He as kes | NOR 0°147 0°461 | Brustein 
ee 1 NAOH | 0-054 0386 
It is still, however, necessary to account for the fact that the 
absorbed bases displace an equivalent amount of some other bases 
from the soil—a procedure which would be unnecessary if nothing 
but adsorption were involved. This is done by supposing that 
only the hydroxide is absorbed: the acid radicle in general is 
not; it therefore dissolves out some of the bases from the soil. 
As this is a purely chemical reaction the amount of base brought 
out is equivalent to the acid set free, 7.e., to the amount of base 
adsorbed. 
20895 C4 
