592 



Journal of Agricultural Research 



Vol. XX, No. 7 



AMOUNT OF WATER-SOLUBLE MATERIAL IN SEEDS AS MEASURED 

 BY THE FREEZING-POINT METHOD 



Recognizing the influence that high concentration of solution has 

 upon the quantity of water that refuses to freeze, the authors always 

 determined the freezing-point depression 1 of the seeds after they were 

 used for the dilatometer measurements. It was found that the magni- 

 tude of this depression was high for most of the seeds. Since the seeds, 

 however, used in the dilatometer measurements were allowed to stand 

 about two days in excess of water and were then subjected to alternate 

 freezing and thawing, it was thought that the depression values obtained 

 were the result of the biological and physical changes that the seeds 

 underwent. In order to ascertain, however, whether the seeds contained 

 water-soluble material in the dry condition they were ground very fine 

 and then portions of 10 gm. were mixed with 20 cc. of water in a 

 freezing-point tube. The mixture was allowed to stand for about 40 

 minutes, and then its freezing-point depression was determined in the 

 usual way. Table III contains the results obtained. The values of the 

 freezing-point depression have also been calculated into osmotic pressure 

 in atmospheres after the table of osmotic pressures worked out by 

 Harris and Gortner. 2 



Tabi.U III. — Freezing-point depression and osmotic pressure of dry seeds when 10 gm. 

 of powdered dry seeds were mixed with 20 cc. of water 



Kind of seeds. 



Spring wheat 



Rye 



Buckwheat 



White corn 



Broom corn 



Sorghum 



Alfalfa 



Alsike clover 



Mammoth clover 



Cowpeas 



Field peas 



Field white beans . . 



Black soybeans 



Speckled wax beans 

 Red kidney beans . . 



The results in Table III are very surprising. They show most strik- 

 ingly that there is a tremendous amount of readily water-soluble material 

 in seeds, and in some seeds much more than in others. Thus the depression 

 varies from 0.280 C. in wheat to 1.180 in speckled wax beans. When 



1 Bouyoucos, George J:, and McCool, M. M. op. cit. 



2 Harris, J. Arthur, and Gortner, Ross Aiken, notes on the calculation of the osmotic pres- 

 sure OF EXPRESSED VEGETABLE SAPS FROM THE DEPRESSION OF THE FREEZING POINT, WITH A TABLE 



FOR the values of p for A = o.ooi° To £ = 2.999°. In Amer. Jour. Bot., v. i, no. 2, p. 75-78. 1914. 



