374 
ming, watering, and the addition of artificial coloring matters and 
preservatives, the addition of thickening agents such as chalk, 
calves’ brains, starch, glycerin, etc., having almost passed out of 
vogue among farmers and dairymen. Indeed it is doubtful whether 
the (3) form of adulteration was ever practiced to any considerable 
extent (1). 
Skimming . — This form of milk adulteration is probably practiced 
among farmers and dairymen to a considerable extent. As its name 
indicates, it consists in the removal, by means of a separator or 
otherwise, of a part of the cream. Obviously, skimmed milk con- 
tains a smaller percentage of milk fat than normal milk, and it was 
with a view of correcting and controlling this particular form of 
adulteration and watering that laws have been enacted in many 
countries and in many States throughout our own country fixing 
the amount of milk fat which a milk offered for sale should contain. 
It will be seen from the compilation of milk standards given on 
page 371 that the amount of fat required in different States varies 
from 2.4 to 3.5 per cent. All things considered, it seems reasonable 
to require that all milk offered for sale should contain at least 3.25 
per cent of fat, although it should be borne in mind, of course, that 
unadulterated milk, especially of certain breeds of cattle, some- 
times contains less than this amount of milk fat. The color of 
skimmed milk is also more or less characteristic, tending more to 
dead white or bluish white than normal milk, which is distinctly 
yellowish white in color. 
Watering . — The addition of water to milk is probably the com- 
monest practice in milk adulteration. Obviously this is done in 
order to increase the output of the herd. The effect of watering is 
to alter the physical properties and chemical composition to a greater 
or less degree, depending on the quantity of water added. The addi- 
tion of water to milk has been found to lower the specific gravity 
and elevate the freezing point of milk. It also lowers the index of 
refraction and probably the viscosity. It causes diminution in the 
amount of fat, total solids, and ash. Ordinarily it is not a difficult 
matter to determine whether a given sample of milk has been watered. 
This is done by comparing its specific gravity and refractometer 
reading, together with the amounts of fat, total solids, and ash, with 
those of. normal milk or with standards which have been based upon 
the results of thousands of analyses and years of experience with 
the milk of different herds of dairy cows and that produced in differ- 
ent countries. In the detection of watered milk advantage is also 
taken of the fact that natural waters frequently contain substances 
not ordinarily present in milk, such as nitrates and nitrites. If these 
substances are found in a sample of milk the chances are that water 
