B. 1'. I.— 759. 



A METHOD FOR THE DETERMINATION OF THE 



SPECIFIC GRAVITY OF WHEAT AND 



OTHER CEREALS.' 



INTRODUCTION. 



In buying and selling wheat great importance is placed on the den- 

 sity of the wheat kernels, the various degi'ees of which affect to a 

 considerable extent the commercial grading and the price that the 

 wheat will command. 



Believing that the specific gravity of wheat might in a measure 

 indicate milling quality, a study of the relationship of specific gravity 

 to milling yield was undertaken. Of a large number of liquids tried 

 in these experiments for specific-gravity determinations, toluene was 

 found to possess more nearly the requhed properties. Toluene 

 (known commercially as toluol), CgHsCHg, possesses the desired prop- 

 erties in that it has (1) relatively low specific gravity; (2) a low 

 surface tension, enabling it to flow smoothly in thin sheets; (3) a 

 fau-ly high boiling point, insuring not too high volatility; (4) physical 

 constants, mcludmg specific gravity, viscosity, etc., that will not 

 change materially on exposure to the atmosphere; and (5) a nonsol- 

 vent action on the constituents of the kernel. It is likewise immisci- 

 ble with water and practically nonexplosive. Toluene was therefore 

 employed with the results set forth in the following pages. 



By employing a liquid medium of this character it is possible to 

 use a specific-gravity bottle, or picnometer. A picnometer of the 

 size and style shown in figure 1 was found to be the most satisfactory. 

 The gi'ound-in thermometer is of decided advantage in making all 

 determinations at the same temperature (20° centigrade). The 

 capillary side tube serves as a convenient overflow for the excess 

 toluene when the bottle is filled at temperatures below 20° C. The 

 small cap is used to cover th(> side tube when the thermometer regis- 

 ters 20° C. and to hold that which passes up this tube as the contents 

 of the bottle reach the room temperature. 



> Since the preparation of this paper one of the writers, Mr. C. n. Bailey, has a,ccepted a position at the 

 University of Minnesota and is now in charge of the cereal and flour laboratory of the Minnesota Agricul- 

 tural Experiment Station. — J. W. T. Duvel, Oop Technologist in Charge of Grain Standardization Investi- 

 gations. 



50Gh2°— Cir. 99—12 3 



