BULLETIN 164, U. S. DEPARTMENT OF AGRICULTURE. 



The ether extract is shaken with a strong solution of sodium bisul- 

 phite, which treatment removes from the ether compounds of an 

 aldehyde nature. After separating the bisulphite from the ether 

 it is acidified with enough sulphuric acid completely to decompose it, 

 is freed from sulphur dioxide by blowing air through it, and is again 

 shaken with ether. The ether extract obtained by this process on 

 evaporation gave an oily residue. The residues secured from the soils 

 taken from the vaniUin-treated plots which had grown cowpeas, gar- 

 den peas, and string beans had the odor of vanillin. The residues 

 were purified according to the method given in the paper cited. 

 An aqueous solution of the purified residue from the three soils 

 smelled strongly of vanillin. The aqueous solutions gave the color 

 reactions characteristic of vanillin. Ferric chloride added to a por- 

 tion of the solution gave a blue-violet color. When boiled with 

 resorcinol and hydrochloric acid a red color resulted. The solution 

 gave a violet color with a mixture of sulphuric and hydrochloric acid 

 and acetone water. Bromine water and ferrous sulphate gave a green 

 color. Or the addition of the reagent of Folin and Denis, the solution 

 having been made alkaline with sodium carbonate, a clear blue color 

 developed. 



As is shown from the above examination that this vanillin- treated 

 field soil still contained the substance, it was tested in pots as to its 

 qualities for growing plants. 



In this experiment wheat was grown in the greenhouse in paraffined 

 wire pots, using the respective soils from the vanillin-treated plot and 

 the check plots which in the field had grown cowpeas, garden peas, 

 and string beans. The plants grew from December 11, 1913, to 

 January 6, 1914. Two pots with 6 plants each were used for each 

 soil. The results of the experiment are given in Table V. 



Table V.- — Growth of wheat in -pots of soil taken from the field -plots six months after 



treatment with vanillin. 





Green weight of wheat plants on — 



Plot. 



Soil from 

 plots un- 

 treated. 



Soil from 



vanillin 



plots. 



Relative 



growth, 



check = 100. 





Grams. 

 1.48 

 1.47 

 1.54 



Grams. 

 1.09 

 1.10 

 1.10 



74 





75 



String bean plot 



71 



The table shows that the soils from the vanillin-treated plots were 

 harmful to wheat in soil collected six months after the vanillin had 

 been applied. 



A similar experiment was made with these soils, except that the 

 crops grown in the pots were identical with those which had grown in 



