New YorK AGRICULTURAL EXPERIMENT STATION. 341 
after each addition of alkali, until a faintiy, but distinctly, 
pinkish shade of color remain even after considerable agita- 
tion. Any marked excess of alkali must be avoided. 
(a) Preparation of color standard.—We have found that 
more uniform and satisfactory results in neutralizing can be 
attained by preparing a color-standard for comparison. Our 
method of accomplishing this is as follows: About 20 ce. of 
fresh skim-milk and 80 cc. of water are put into a 200 cc. flask 
and a small amount of mercuric chlorid added to prevent 
souring. <A few drops of ordinary carmine ink are consider- 
ably diluted with water and this is carefully added, a few 
drops at a time, to the diluted skim-milk until a faint but 
distinct pinksh coloration appears. This can be more readily 
and accurately perceived by placing beside the flask another 
flask half full of uncolored diluted skim-milk. The coloration 
must be as slight as possible and yet be appreciably distinct 
when compared with uncolored milk. After the color-standard 
has been prepared, the flask is stoppered. It is well to keep 
this standard in a dark place when not in use. With some 
carmine colors, the pinkish shade in the milk deepens on 
standing, especially when exposed to light, and with others 
it may fade. If at any time a deeper shade is observed, the 
proper shade can be reproduced by slight dilution with skim- 
milk; in case of fading, the additon of one or more drops of 
carmine ink is needed. The object of using skim-milk in pre- 
paring a color-standard is to avoid the presence of fat which, 
in case of whole milk, separates on standing, adheres to the 
sides of the flask and obscures the color. 
(b) Use of color-standard.—In neutralizing a sample of 
milk, the color-standard is placed beside the sample under 
examination fer constant comparison after each addition of 
alkali. The flasks should be placed on a white surface and 
in a good light in order to render more sharp the observation 
of the coloration. In fresh milks, it is usually found that 3 
or 4 ce. of alkali is sufficient to neutralize the milk. In cases 
where milk is not strictly fresh or where it has been kept 
