THE COMPOSITION OF FEEDING STUFFS 17 
___5. Fat.—The residue from the preceding determination is extracted 
with anhydrous sulfuric ether in a:suitable apparatus for a considerable 
period of time, generally 16 hours, till the fat has been completely dissolved, 
The ether is distilled off and the residue dried at 100° C. and weighed. 
As previously stated, the ether extract, in the case of roughage and some 
other feeds, contains considerable impurities, as chlorophyl, wax, and 
resins. 
c. Protein is obtained by multiplying the total nitrogen by 6.25 (see 
p- 9), the nitrogen being determined by the Kjeldahl method, so called 
after the inventor, a Danish chemist. In this method a small portion of 
the feed (generally 1 gram) is heated with 20 cc. sulfuric acid till the 
organic matter has been completely decomposed and the nitrogen has been 
changed into ammonium sulfate. This is dissolved in distilled water, 
Fre. 5.—View of a chemical laboratory for analysis of feeding stuffs and other agricultural 
products. (Wisconsin Station.) 
and 50 ¢.c. of a concentrated soda solution are added, the flask being 
connected with a distillation apparatus and heat applied. A certain 
quantity of standard hydrochloric acid solution, more than sufficient’ to 
neutralize the: ammonia obtained in the oxidation of the protein, has been 
previously added in the receiving flask, and the distillation is now con- 
tinued till all ammonia has been distilled over. The excess of acid in the 
receiving flask is then accurately titrated back We eel and from the 
volume of acid used the amount of nitrogen in the sample is obtained. 
This is calculated in percentage of the amount of sample weighed out, 
and by multiplying by 6.25 the percentage of protein contained in the 
sample is obtained. F 
d. Fiber is determined in the residue from the fat extraction by boiling 
first with 200 c.c. of a 1.25 per cent sulfuric acid solution and then with 
200 e.c. of a soda solution of the same strength. After filtering, drying, and 
weighing, the residue is ignited, and the loss in weight, calculated on the 
amount of the sample originally weighed out, shows the percentage of 
