CHAPTER VI 

 THE COLLOIDAL MATTER OF THE SOIL ^ 



Eesearch in physics and physical chemistry is each day 

 making it clearer that the properties of matter are by no 

 means entirely determined by chemical composition. Matter 

 varies in its physical character and its chemical activities with 

 its fineness of division. Coarsely divided substances function 

 much differently when they become molecular complexes and 

 still more diversely when their aggregates are divided into 

 their molecular and ionic components. Because of the par- 

 ticular properties exhibited by material in a fine state of di- 

 vision, approaching but not attaining a molecular simplifica- 

 tion, a special name is utilized. A substance in such a con- 

 dition is said to be colloidal or in the colloidal state. 



68. The colloidal state ^ arises when one form of matter 

 (either a gas, liquid, or solid) in a very fine state of division 



* Colloidal chemistry is now so well understood that it will be n-ecessary 

 to develop only those phases which have a direct bearing on soil 

 phenomena. 



^Some of the following general references may prove helpfnl: 



Eamann, E., KolloidstudAen hei Bodenlmndhchen Arbeiten; KoUoid- 

 chemische Beihefte; Band II, Heft 8/9, Seite 285-303, 1911. 



Mklas, H., Die Kolloidchemie und ihre Bedeutung fur BodenTcunde, 

 Geologie, und Mmeralogie ; Internat. Mitt, fiir Bodenkunde, Band II, 

 Heft 5, Seite 383-403, 1913. 



Bancroft, W. B., The Theory of Colloid Chemistry; Jonr. Phys. Chem., 

 Vol. 18, No. 7, pp. 549-558, 1914. 



Taylor, W. W., The Chemistry of Colloids; ISTew York, 1915. 



Burton, E. E., The Fhysical Properties of Colloidal Solutions; London, 

 1916. 



Zsigmondy, E., The Chemistry of Colloids, Part I; trans, by E. B. 

 Spear, New York, 1917. 



Wiegner, G., Boden und Bodenhildung ; Dresden and Leipzig, 1918* 



Bancroft, W. D., Applied Colloidal Chemistry; New York, 1921. 



Thatcher, B. W., Chemistry of Plant Life; Chap. XV, New York, 1921. 



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