12 BULLETIN 1166, U. S. DEPARTMENT OF AGRICULTURE. 
Ether extract (crude fat) was determined by the official method, 
Doth without previous extraction of the material with cold water and 
after such extraction and subsequent drying. The higher results, 
obtained without extracting with water, are the ones reported. 
Crude fiber. — Properly prepared asbestos was mixed with the 
charge in both the acid and alkali digestions. This was practically 
necessary because of the slowness of filtration. Even with the 
asbestos present and serving to render the residue more porous, the 
second filtration, after the alkali digestion, was very slow. 
Nitrogen-free extract. — The percentage of nitrogen-free extract 
was obtained by subtracting the sum of the moisture, crude protein, 
ether extract, crude fiber, and ash percentages from 100. 
Reducing sugars and sucrose. — The Bryan-Given-Straughn method 
for total (reducing and nonreducing) sugars, applicable to cattle 
foods (7), was followed, but it was modified in the case of the initial 
charge and the aliquots used. 
Starch was determined by the official malt diastase method, modi- 
fied as follows : Twenty-five per cent alcohol, instead of 10 per cent 
alcohol, was used for extracting sugars and other interfering soluble 
carbohydrates. For the first digestion of the gelatinized starch with 
malt extract, after adding the infusion the temperature was raised 
gradually to 70° C. instead of 55° C. and maintained at this tempera- 
ture for 30 minutes, the total time of heating being about 1 hour. 12 
After the acid hydrolysis, phosphotungstic acid solution 13 was added 
to defecate the cold acid dextrose solution. When it had been fil- 
tered to eliminate precipitated impurities, an aliquot was neutralized, 
after which the usual procedure was followed. 
Recent work on the determination of starch in the presence of 
interfering polysaccharides, such as pectin, has indicated that cor- 
rect results may be obtained by using 60 per cent alcohol to elimi- 
nate the interfering substances. Immediately after the malt diges- 
tion alcohol is added, a little at a time, with constant mixing, until 
the concentration reaches 60 per cent. An aliquot of the filtrate is 
evaporated over steam until the aqueous residue is practically free 
from alcohol. This residue is taken up with hot water and sub- 
jected to acid hvdrolvsis, etc. (J. Agr. Research, vol. 23, No. 12 
(1923), p. 995)./ 
Degree of acidity (total titrable acidity) was determined on a 
water extract and on an 80 per cent alcohol extract of the material, 
essentially following the tentative method of the Association of Offi- 
cial Agricultural Chemists (7). The extracts were obtained by vio- 
lently stirring the charge and solvent in a four-sided 8-ounce glass 
jar for 30 minutes by means of an electric mixer. 14 In the case of 
the water extract, distilled water, previously boiled and cooled, was 
used. The total acidity, expressed as cubic centimeters of normal 
" acid " per kilogram of material, is termed the " degree of acidity." 
Specific acidity (hydrogen-ion concentration) of the water and 
alcoholic extracts. — The specific acidity (hydrogen-ion concentra- 
12 While the conversion of starch into sugars is not as complete by this procedure as by- 
digestion at 55° C, the starch is rendered soluble much more effectively, and with the 
second digestion conducted at 55° C, as in the original method, uniformly better results 
have been obtained in the Bureau of Chemistry. 
13 Two cubic centimeters of a 10 per cent solution of ohosphotungstic acid in 1 per cent 
hydrochloric acid. 
" Described in U. S. Dept. Agr. Off. Sec. Circ. 68. 
