MILLING AND BAKING TESTS OF WHEAT. 



while the average specific gravity of a number of samples of hard 

 wheat was 1.4273, the range being from 1.4152 to 1.4427. 



Roberts 1 found a range in specific gravity between 1.227 and 1.386 

 in tests with 52 different types of wheat. 



In his studies of various kinds of seeds Nobbe 2 gives the average 

 specific gravity of 30 samples of wheat as 1.4131, with a variation 

 between 1.3766 and 1.4396. The specific gravity of various other 

 seeds is also given, viz, corn cockle (Agrostemma githago), 1.233; rye, 

 for different tests, 1.325 and 1.371; barley, 1.351. The specific 

 gravity of different species of vetch (Vicia) is given as follows : Vicia 

 benghalensis, 1.344; Vicia dumetorum, 1.203; Vicia 1 'aba, 1.298; Vicia 

 lutea, 1.273; Vicia monanthos, 1.327; Vicia narbonensis, 1.300. 



Table II gives a comparison of the specific gravity of wheat with the 

 specific gravity of several impurities very frequently found in wheat. 

 These figures represent but one test of the impurities used in the milling 

 and baking tests described in the following pages. It will be noted 

 that the corn-cockle seed has a specific gravity nearly equal to that 

 of wheat, while rye and hairy vetch have a greater specific gravity 

 than wheat. The samples of rye, barley, kafir, and hairy vetch 

 were cleaned with a small milling separator to remove any foreign 

 matter, such as chaff or dirt, and the small and light kernels were also 

 removed. The samples of rye and hairy vetch were possibly above 

 the average quality. This is indicated by the test weight per bushel 

 after the samples were cleaned. The rye weighed 58 pounds and the 

 hairy vetch 64 pounds per bushel in comparison with 57 pounds per 

 bushel, the test weight of the wheat used in the various tests with the 

 different impurities. The kinghead seed, though having a smaller 

 specific gravity than wheat, is somewhat larger and is not readily 

 removed with ordinary mill cleaning machinery. 



Table II.- — Specific gravity of wheat and of certain impurities frequently found. 



Wheat and im- 

 purity. 



Sp.gr. 



Impurity. 



Sp. gr. 



Impurity. 



Sp.gr. 



Impurity. 



Sp. gr. 



Wheat (spring). . 

 Rye 



1. 3992 

 1. 4097 





1. 3425 

 1. 3320 





1. 3175 

 .9563 



Corn cockle 



Hairy vetch 



1. 3915 



Wild oats 



Kinghead 



1.4888 







Figure 1 shows the comparative size and shape of wheat and rye 

 kernels and of seeds of corn cockle; hairy vetch, kinghead, and wild 

 vetch. 



METHODS OF PREPARATION AND MILLING. 



To insure greater uniformity in the different tests, a sufficient 

 quantity of wheat of one variety was purchased each year to make all 

 the milling tests desired. Thus, the samples milled and used as 



1 Roberts, H. F. Breeding for type of kernel in wheat. Kans. Agr. Exp. Sta. Bui. 170, p. 108-114, 1910. 



2 Noble, Friedrich. Handbuch der Samenkunde, p. 315-319. Berlin, 1876. 



