A REVIEW OF METHODS FOR THE ISOLATION AND 



IDENTIFICATION OF THE ORGANIC CON- 



STITUENTS OF SOILS 



A. W. THOMAS 



Various studies of growth in heated soils, conducted under Dr. 

 Gies' guidance in this laboratory and at the N. Y. Botanical Garden, 

 have indicated that soils subjected to high temperatures gain or 

 lose in their capacity to sustain the growth of various plants and 

 fungi (see the preceding paper).^ Does high temperature increase, 

 in soils, the proportion and availability of nutrients or does it 

 merely decrease the toxic power of, or remove, contained deleterious 

 agents? If nutrients are increased, in soils, by the application of 

 high temperatures, are the nutrients organic substances or inorganic 

 products ? 



With a view of ascertaining whether the proportions of some 

 of the leading organic substances may be increased, in a soil, under 

 such conditions, and whether organic substances are produced de 

 novo or whoUy removed, I have applied to a soil, at Dr. Gies' Sug- 

 gestion, the methods of Schreiner for the Isolation and detection of 

 organic constituents (see page 313 of this issue).^ For the benefit 

 of readers of the Biochemical Bulletin who may desire a brief 

 and easily accessible summary of these valuable methods, I have 

 prepared the following review of them.^ 



Five kilos of soil, carefully sifted through a 2 millimeter sieve 

 to remove stones, roots, insects, etc., are treated in a glass stoppered 

 bottle with 15 liters of a 2 per cent sol. of sodium hydroxide for 48 

 hours with frequent shaking for the first 40 hours. 



1 Wilson : Biochemical Bulletin, 1914, iii, p. 202. 



2 Thomas : Biochemical Bulletin, 1914, iii, p. 313. 



3 Schreiner and Shorey: Chemical nature of soil organic matter. Bull. No. 

 74, U. S. Dep't of Agric, 1910; Schreiner and Shorey: Examination of soils for 

 organic constituents, especially di-hydroxy stearic acid, Bull. No. So, U. S. Dep't 

 of Agric, 1911. 



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