422 



Biochemical Studies of Heated Soils 



[Mar. 



tate which became lighter in color with each successive addition. 

 This precipitate was removed by filtration and the clear yellow 

 filtrate was saturated while hot with hydrogen sulfid. This was 

 also done with suspensions of each of the two precipitates already 

 obtained. The lead was removed as sulfid and the excess of hydro- 

 gen sulfid was boiled out. The three purified solutions were tested 

 as follows, with the results indicated : 



Material precipi- 

 tated by normal 

 lead acetate . . . 



Material precipi- 

 tated by basic 

 lead acetate . . . 



Material precipi- 

 tated by 

 neither reagent . 



Molisch Test 



W 7 eak 



Very strong 



Very strong 



Fehling-Bene- 

 dict Solution 



Reduction (?) 



Reduction 



Reduction (?) 



Alkaline Silver 

 Solution 



Reduction 



Reduction 



Heavy pre- 

 cipitate 



Color 



Brown 



Brown 



Light yellow 



Odor 



Sharp 



Sweet 



Sweet 



Note. An attempt was made to prepare osazones from the solutions by the 

 customary use of phenyl hydrazine and sodium acetate but dark amorphous 

 products were always obtained. 



The three solutions obtained, as described in the last paragraph, 

 from the basic lead acetate precipitate, the normal lead acetate pre- 

 cipitate, and the final filtrate, were all evaporated to small bulk. 

 With these solutions various attempts to make separations were 

 ineffectual until we found that the addition of an alcohol-ether mix- 

 ture or acetone produced light nocculent precipitates. Acetone 

 yielding better results, we used it upon larger volumes of the three 

 solutions. The acetone produced buff-colored precipitates of great 

 bulk but containing little material when dry. They dissolved easily 

 in distilled water. Such solutions showed little if any reduction of 

 Fehling-Benedict solution, but gave strong Molisch tests in all 

 cases. They gave reddish brown colorations with dilute solutions 

 of iodin with potassium iodide. 



From these chemical observations, then, it seems likely that the 

 organic material in heated soil extracts consists mostly of carbo- 

 hydrate-like substances, probably derived from the cellulose remains 

 of previous plant growth upon the soil. Whatever may be the 



