120 Phenomenon of Absorption in its Relation to Soils 



to trace the development of his ideas. In his first paper^ he investigated 

 the relationship between the amount of absorption and the easily 

 decomposable silicates of the soil. Here he followed Way's earlier 

 assumption as to the seat of the absorptive power of the soil and the 

 later results that many natural "zeolotic" silicates, basalt, natrolite, 

 etc., showed similar phenomena when brought into contact with salt 

 solutions (Eichhorn^, Lemberg^). Heyden'* had shown that a soil after 

 treatment with hydrochloric acid gives up silica to a solution of caustic 

 soda. Van Bemmelen regarded the amount of silica thus liberated 

 as an indication of the quantity of easily decomposable silicates present. 

 He generally found that soils which absorbed well also gave up much 

 silica. After a soil had been boiled with hydrochloric acid, it took up 

 only small quantities of potassium from a solution of neutral potassium 

 salt but large quantities from the hydroxide or carbonate solutions. 

 If such a soil were first treated with sodium hydroxide, then it would 

 react normally with neutral potassium salts, potassium being taken up 

 and sodium appearing in the solution. These reactions were attributed 

 to the silica "gel" present in the soil after boiling with acid. 



He concludes that soil absorption is a chemical and not a physical 

 phenomenon, basing his conclusions chiefly on the fact that an exchange 

 of bases always takes place. 



In subsequent papers his opinions change. This later work is 

 chiefly on absorption by simple gels, e.g. of silica, tin oxide, iron oxide 

 and alumina. He found that neutral salts and acids were absorbed 

 by silica in small quantities; in this case there could be no possibility 

 of chemical reaction. He thus recognises the possibility of physical 

 absorption of hydroxides and carbonates by silica and where substitu- 

 tion takes place he says that the substitution is not really chemical 

 but only apparently so^. In 1900^ he definitely stated that if any 

 absorbent is in equilibrium with a solution of a substance C^ and a 

 second substance C^ is brought into the solution, then partial sub- 

 stitution of C'l by C2 will take place. Van Bemmelen thus partially 

 removed aluminium chloride from a silica gel, sulphuric acid from a 

 manganese dioxide gel and calcium chloride from a chromium hydroxide 

 gel by means of potassium chloride and potassium sulphate, 



1 Ber. Deut. Chem. Ges. 1878, 11, 2228; also Landw. Versuchs-Stat. 1878, 23, 265. 



2 H. Eichhorn, Landw. Jahrb. 1875, 4, 1. 



' J. Lemberg, Zeits. d. deutschen geol. Ges. 1883, 35, 557. 

 * Ann. d. Landw. 1864, 43, 310. 



' Die Absorption, p. 100; Landw. Versuchs-Stat. 1888, 35, 67. 

 « Ibid. p. 441; Zeits. f. anorg. Chemie, 1900, 23, 321. 



