84 MILK PRODUCTS 
is allowed to run into an Erlenmeyer flask, with 
care not to let fat globules pass. Hot water is 
again added to the beaker, and the extraction 
is repeated from ten to fifteen times, using each 
time from 10 to 20 c.c. of water. The resulting 
washings contain all but a mere trace of the salt 
originally present in the butter. The chlorin is 
determined volumetrically in the filtrate by 
means of standard silver nitrate and potassium 
chromate indicator and calculated to sodium 
chlorid. 
Butter-substitutes.—The chief adulteration of 
butter consists in the substitution of foreign fats, 
especially the product known as oleomargarin. 
When fats are saponified and the soap treated 
with acid, the individual fatty acids are obtained. 
It is upon the recognition of the peculiar acid 
radicles existing in butter that the most satis- 
factory method of distinguishing it from other 
fats is based. Since the relative proportion of 
these radicles differs in different samples, the 
quantitative estimation cannot be made with 
accuracy; but when the foreign fats are substi- 
tuted to the extent of 20% or more, the adultera- 
tion an be detected with certainty and an 
approximate quantitative determination made. 
The detection of adulteration of butter-fat by 
other fats is generally carried out by the deter- 
