THE ABSORPTIVE PROPERTIES OF SOILS 355 



to dissolve one part of absorbed ammonia from the 

 soil. 



254. Influence of size of particles. — The surface area 

 of the soil particles determines to some extent the amount 

 of substance absorbed. For this and other reasons, a 

 fine-grained soil absorbs a greater quantity of material 

 than a coarse-grained soil. In fact, it was early shown by 

 Way * that the phenomenon of absorption is largely a 

 function of the silt, clay, and humus of the soil. 



255. Causes of absorption. — A number of causes 

 have been assigned for the absorption of substances by 

 soils, and there can be no doubt that the phenomenon is 

 not due to any one process. Several distinct causes are 

 now very generally recognized, while others that have 

 been suggested may have a part in the result. 



256. Zeojites. — As the result of his extended researches 

 on absorption of soils, Way concluded that the property 

 of absorption, or fixation of bases, rests largely with the 

 hydrated silicates of aluminium, containing calcium or 

 magnesium and one of the alkali metals, these compounds 

 being known as zeolites. He prepared artificially a 

 hydrated silicate of aluminium and sodium, and found 

 that by treating this with a solution of a calcium salt 

 he could replace most of the sodium, obtaining thereby 

 a silicate of aluminium, calcium, and part of the sodium 

 that was originally contained in the silicate. The re- 

 mainder of the sodium could be replaced by potassium 

 from solution and, likewise, by magnesium and ammonium. 



1 Way, J. T. On the Power of Soils to Absorb Manure. 

 Jour. Royal Agr. Soc. England, Vol. 11, pp. 313-379. 1850. 

 Also, On the Power of Soils to Absorb Manure. Jour. Royal Agr. 

 Soc. England, Vol. 13, pp. 123-143. 1852. Also, On the 

 Influence of Lime on the " Absorptive Properties " of Soils. Jour- 

 Royal Agr. Soc. England, Vol. 15, pp. 491-515. 1854. 



