68 THE SOII, SOLUTION 



Liebreich, Becquerel, Lieving and other investigators. So-called 

 "contact reactions," as in the production of sulphuric acid, are 

 now familiar processes rinding commercial applications. And 

 the solubility of some substances at least, notably gypsum, has 

 been shown to vary considerably with the size and consequent 

 shape of the particles in the solid substance in contact with its 

 solution. 1 



It has been shown that some soils will at times produce the 

 blue coloration in alcoholic solutions of guiac, which is char- 

 acteristic of oxidases, and yellow aloin solutions are sometimes 

 colored red. Hydrogen peroxide is decomposed by some soils 

 even after they have been thoroughly ignited to get rid of all 

 organic matter. But in how far these effects may be due to 

 surface influences can not be positively stated; yet uncompleted 

 investigations by Dr. M. X. Sullivan indicate that some of these 

 phenomena at least must be attributed to specific influences 

 (although probably of catalytic character) of particular soil 

 components, such possibly as manganous oxide or ferric oxide; 

 but the mechanism of the reactions is as yet largely speculative. 



The soil is composed in large part of very fine particles of 

 rounded shape, exposing relatively an enormous surface to the 

 soil solution, and normally this solution is mainly under capillary 

 conditions, so that we should expect that many reactions would 

 take place quite differently in the soil from the way they would 

 in a beaker or flask. This fact has been generally overlooked 

 or ignored, and is probably the explanation of many of the 

 apparently anomalous results hitherto reported in chemical invest- 

 igations of soils. Abnormal solubilities, precipitations, oxida- 

 tions or reductions are frequently found in the literature, and 

 when their abnormality is noted at all, they are too often and 

 with slight show of reason ascribed to indefinite bacterial action 

 or more mysterious vital agencies. Many of them are undoubt- 

 edly the results of surface actions. Unfortunately, aside from 

 1 See especially, Beziehungen swischen Oberflachenspannung und Los- 

 lichkeit, von G. A. Hulett, Zeit. Phys. Chem., 37, 385-406 (1901) ; Loslich- 

 keit und Loslichkeits Beeinflussung, von V. Rothmund, p. 109 (1007) ; 

 Principles theoretiques des methodes d'analyse minerale, par G. Chesneau, 

 pp. 16-25 (1906). 



