r/k 
UNITED STATES DEPARTMENT OF AGRICULTURE 
DEPARTMENT BULLETIN No. 1460 
Washington, D. C. 
December, 1926 
TESTING WHEAT FOR PROTEIN WITH A RECOMMENDED METHOD FOR 
MAKING THE TEST 
By D. A. Coleman, H. C. Fellows, and H. B. Dixon, Chemical Research Labora- 
tory, Grain Division, Bureau of Agricultural Economics 
CONTENTS 
Page 
Introduction 1 
Protein tests by various laboratories 2 
Digestion studies 4 
Acid necessary for digestion of wheat 
samples 6 
Efficiency of heat and catalytic agents on 
oxidation of wheat samples by sulphuric 
acid 9 
Influence of size of sample digested on pro- 
tein test results 12 
Influence of method, time, and sample on 
protein test results 12 
Sampling studies 15 
Effect of duplicate car samplings on protein 
test results 15 
Cleaning samples before analysis 16 
Taking out thesubsample__/_ 17 
Correct size of sample to grind 17 
Care of grinding apparatus 18 
Page 
Sampling studies— Continued 
Influence of fineness of division of sample 
on protein test results 1* 19 
Influence of moisture content of sample on 
protein test results 20 
Distillation technique 22- 
Choice of receiving acids 23 
Mercury precipitants 23 
Standard solutions 23 
Standard method recommended for making 
protein tests 26 
Procuringthe sample 26 
Removing the dockage 26 
Dividing sample for test 26 
Chemical reagents necessary for making 
protein tests 27 
Apparatus 29 
Determination 29 
Special points for consideration 30 
INTRODUCTION 
During the last few years the protein content has become of in- 
creasing importance in determining the price paid for any partic- 
ular grade of wheat. It has not been uncommon for grain firms to 
pay a premium of 5 to 20 cents per bushel over the prevailing option 
for wheat containing a high percentage of protein. One case is 
known where wheat containing 18.6 per cent of protein brought 65 
cents per bushel premium over ordinary wheat of the same numerical 
grade but which contained only 11.5 per cent of protein. When the 
supply of high-protein wheats is plentiful the premiums for high 
protein are much less than when the supply of such wheat is scarce. 
The Grain Market Review for March 13, 1926, issued by the United 
States Department of Agriculture, quoting average prices for wheat, 
states that " hard red spring wheat on the Minneapolis market sold 
at about 12 to 15 cents over the May price for 12 per cent protein Xo. 
1 dark northern. Twelve and one-half per cent protein was quoted 
13754°— 26 1 
