MILLING AND BAKING TESTS OF WHEAT. 3 
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 giihago), 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 faba, 1.298; Vicia 
lutea, 1.273; Vicia monanihos, 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 
Kafir 
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. Eul. 170, p. 108-114, 1910. 
2 Noble, Friedrich. Handbuch der Samenkunde, p. 315-319. Berlin, 1876. 
