June 23,1923 
Protein Percentage of Wheat, Oats, and Barley 
1043 
PlyAN OF BXPFRIMKNT 
Marquis wheat, Improved Ligowa oats, and Manchuria barley were 
grown in 17 localities in the United States during the years 1920 and 
1921. The grains were grown at experiment stations and substations in 
eight States which represent extremes, so far as the quality of grain pro¬ 
duced is concerned. The seed was sent to each station from University 
Farm, St. Paul, Minn., each year, so that the seed planted would be iden¬ 
tical. Plantings were made at the regular planting time in the spring 
and harvested when the grain was mature. Samples of the crop in each 
instance were sent to University Farm, where nitrogen determinations 
were made for total protein. 
During the summer of 1921, respiration studies were made upon these 
grains during the ripening or desiccation period at University Farm, to 
ascertain the amount of material lost during this time. The studies were 
started when the grains reached the dough stage, before the desiccation 
process of maturity had begun, and continued until complete maturity. 
Each morning at 8 a. m. samples of head material of each of the grains 
were collected, placed in an air-tight container, and taken to the labor¬ 
atory. Twenty-five grain samples 'were picked from the spike by hand 
and immediately placed in a respirometer. The grains were subjected for 
2 hours to a temperature of 30*^ C., after which the carbon dioxid respired 
was swept through the modified Truog absorption tower and collected 
in saturated barium hydroxid solution. The carbon dioxid evolved in 
this time was calculated in milligrams by titration with N/10 hydrochloric 
acid and computed into carbon dioxid lost per 100 gm. of dry matter in 
24 hours. 
Table I shows the results of this work. It should represent the maxi¬ 
mum loss by respiration which could be expected under field conditions. 
A constant temperature of 30° C. would average the high rate of respiration 
during the heat of the day and the lower rate during the cool night time. 
Table I shows the amount of carbon dioxid produced and the actual 
amount of carbohydrate material lost from the grain, per 100 gm. of 
dry matter, in the process of respiration throughout the 16-day ripening 
period. The amount of carbohydrate material lost was calculated from 
the data showing the carbon dioxid evolved. The evolution and estima¬ 
tion of carbon dioxid is probably the most accurate method of determin¬ 
ing the loss in weight due to oxidation, and is intended to account for the 
entire collective activities of respiration. While the process of respira¬ 
tion is a complex one, and it is impossible to account for the exact changes 
which take place, the carbohydrate material lost can be very closely 
estimated by assuming the process in general to be oxidation of sugars 
and starch. 
The oxidation process results in the formation of carbon dioxid and 
water according to the empirical formula, C6Hio05 + Oi2-~>6C02 + 5H20. 
One part of carbohydrate with a molecular weight of 162 when oxidized 
by free oxygen, results in the formation of 6 molecules of carbon dioxid 
with an equivalent weight of 264. From these figures it will be seen 
that the formation of 100 gm. of carbon dioxid will require 61.36 
gm. of carbohydrate material. Thus, the amount of carbohydrate lost 
is calculated as 61.36 per cent of the carbon dioxid evolved. For 
wheat this gives a loss of 10.038 gm.; oats, 11.092 gm.; and barley, 15.12 
gm. of carbohydrate per 100 gm. of dry matter in 16 days, as indicated 
in Table I. 
