356 



Scientific Proceedings (123). 



172 (1919) 



A method for the estimation of the hydrophilic colloid content 

 of expressed plant-tissue fluids. 



By ROBERT NEWTON and ROSS AIKEN GORTNER. 



[From the Division of Agricultural Biochemistry, University of 

 Minnesota, St. Paul, Minn.] 



The freezing-point depression of the freshly expressed plant 

 juice is first obtained. Then, having determined the total solids 

 by the refractometric method described by Gortner and Hoffman 

 in the preceding note, a quantity of sucrose just sufficient to make 

 a molar solution in the total water present is added. The freezing- 

 point depression is again determined, and is usually found to have 

 increased more than the theoretical amount (2.085 0 , allowing for 

 the formation of sucrose hexahydrate). 



It is assumed that the magnitude of the excess depression is a 

 measure of the quantity of water held in such a way as to be un- 

 available for the solution of the sugar. This has been found to 

 correspond in a general way with the content of hydrophilic col- 

 loids, as indicated by viscosity measurements, and proved by 

 dialysis of the juice where this has been carried out, as well as by 

 the preparation of colloidal solutions of known composition. 

 Preliminary experiments with gum arabic indicate a close rela- 

 tionship between the "bound" water and the concentration of the 

 added colloid. 



It seems probable that the method may be applied to any bio- 

 logical fluid. A more detailed account of the experiments will be 

 published in a botanical journal. 



173 (1920) 



Calcium phosphate metabolism showing the prevention of rickets 

 by feeding clear grades of flour. 



By J. F. McCLENDON. 



[From the Laboratory of Physiological Chemistry, University of 

 Minnesota, Minneapolis, Minn.] 



In the milling of flour the ideal seems to have been production 



