ON COLLOID CHEMISTRY AND ITS INDUSTRIAL APPLICATIONS. 7Y 
by Sjollema, Endell, Ashley, Kénig, Hasenbiumer and Hassler, 
Hanley and Tadokoro, the last named giving other references 
also. Methods depending on the absorption of water vapour have 
been suggested by Mitscherlich. Different methods do not give 
altogether concordant results, nor is it to be expected that they 
should; it is highly improbable that any sharp dividing line 
exists in the soil between the typical colloids and the typical non- 
colloids; intermediate substances are to be expected showing 
colloidal properties only to a slight extent. It is certain, how- 
ever, that the finer particles of the soil—the clay and fine silt— 
show much more marked colloidal properties than the coarser 
particles—the coarse silt and the sands. 
The Constitution of the Soil. 
Soil consists mainly of disintegrated and decomposed rock frag- 
ments of all sizes, varying from 1 mm. diameter downwards; these 
may be said to constitute its skeleton. Intimately mingled with 
these are the decaying remains of past\ vegetation. It seems 
necessary further to suppose that the particles are coated with a 
gel composed of silica, oxides of iron and aluminium, soluble 
organic matter, and a smaller quantity of lime, magnesia and 
potash, traces of ammonia, etc.: this gel being spread relatively 
more thickly on the small particles than on the larger ones. This 
view of the constitution of the soil fits in with the known facts, 
and it has the further advantage of offering a definite starting 
point for further investigations. 
BIBLIOGRAPHY. 
GerproITz, K. K. (Reprints), Chem. Soc. Abstracts, 1918, i. 519 and ii. 364. 
ROTHMUND, v., and KornFELD, G., Zeitsch. Anorg. Chem. 1918, 103, 129-163. 
I.—Soil Absorptions. 
Way, J. T., ‘On the Power of Soils to Absorb Manure, Journ. Roy. Agric. Soc., 
1850, xi. 313-79 ; ibid, 1852, xiii, 123-43. 
LizBiec, Justus, ‘Natural Laws of Husbandry,’ 1863. 
Kwnop, ‘Lehrbuch der Agrikultur Chemie,’ Leipzig, 1868. ‘Die Bonitirung der 
Ackererde,’ 1871. 
BEMMELEN, JAKOB M. VAN, ‘Die Absorptionsverbindungen und das Absorptions- 
vermégen des Ackererde,’ Landw. Versuchs-Stat. 1888, xxxv. 67-136. ‘Das 
Absorptionsvermégen der Ackererde,’ ibid. 1878 (28), 265-304. ‘ Die Absorption 
von Wasser durch Ton,’ Zeit. Anorg. Chem. 1904, xlii, 314-24. 
WIEGNER, GEORG, ‘Zum Basenaustausch in der Ackererde,’ Journ. f. Landw., 1912, 
Ix. 110-150, 197-222. 
Haaser, G., J. Landw., 1917 (65), 245-311 (a paper on the absorption of lime by 
soil). 
: II.—The Soil Solution. 
Moraan, J. F., Soil Science, 1917 (8), 531. 
RAMANN, G., MArz,S., and BAuER, H., Int. Mit. Bodenkunde, 1916 (6), 27. 
Zyu, J. P. van, J. Landw., 1916 (64), 201. 
Nourse, O., ibid., 1917 (65), 1. 
Ill.— Action of Acids on Soil. 
RussE.L, E. J., and Prescott, J. A., ‘The Reaction between Dilute Acids and the 
Phosphorus Compounds of the Soil,’ Journ. Agric. Sci., 1916 (8), 66-116. 
HANLEY, J. A., Nature, 1914 (93), 598. 
KULLENBERG, Jahrbucher Agric. Chem., 1865 (8), 15. 
