2 BULLETIN 102, U. S. DEPARTMENT OF AGRICULTURE. 
meyer flask, then add 50 c. c. of 80 per cent alcohol, specific gravity 
0.86, and stop the flask tight with a cork or rubber stopper. In 
order that the meal may be thoroughly and equally subjected to the 
action of the alcohol, carefully shake the flask with a whirling motion, 
avoiding a distribution of the meal on the sides of the flask. After 
shaking, let the meal digest in the alcohol over night (approximately 
16 to 18 hours). After digestion filter through a dry filter paper. 
Place 25 c. c. of the clear filtrate in a 250 c. c. beaker and add 75 
c. c. of distilled water and 1 c. c. of phenolphthalein solution and 
titrate with a one-hundredth normal alkali solution. The proteids 
dissolved in the alcohol are thrown out of solution when water is 
added, leaving a white precipitate, which makes it difficult to deter- 
mine just what constitutes an end point in the titration . The end 
point that has been adopted is perhaps a slight degree over the point 
of neutrality, but it is necessary to carry the titration to a distinct 
color in order to get comparable results. This titration, as will be 
readily seen when making the determination, is different from most 
titrations, owing to the cloudy white precipitate formed on the addi- 
tion of water to the alcoholic extract, which in a measure obscures 
the color. It will, however, be necessary to analyze corn ranging in 
color from pure white to deep yellow, where in each case the color of 
the extract is slightly different. One also has to deal with mixtures 
of white and yellow corn, where again another colored extract results, 
depending upon the relative quantity of white and yellow corn pres- 
ent in the sample. Plate I will help persons who perform this analysis 
for the first time to get the correct color. The colors shown repre- 
sent titrations of yellow, mixed, and white corn, and it will be seen 
that the color of the liquid obtained at the end point is slightly 
different in each of the three cases. It is not expected that persons 
making this test shall match these colors exactly, but they are 
intended to give one as clear an idea of the color as can be shown on 
paper. 
To correct the reading of the burette for the acid contained in the 
alcohol and phenolphthalein, make a blank by taking 25 c. c. of 
alcohol, 75 c. c. of distilled water, and 1 c. c. of phenolphthalein 
solution and titrate in the same manner as the corn extract. Sub- 
tract the reading thus obtained from the reading obtained by titrating 
the corn extract, and the result will represent the true acidity in 5 
grams of corn. Multiply this result by 2, and it will represent the 
number of cubic centimeters of one-hundredth normal alkali required 
to neutralize the acid in 10 grams of corn, or the number of cubic 
centimeters of normal alkali required to neutralize the acid in 1,000 
grams of corn, This result is termed the " degree of acidity" of the 
corn. 
