If the color
is of a yellowish tinge throughout, the addition of coloring matter
must be suspected. "Annatto," a vegetable pigment, is used to give a
"rich" tint to milk. To detect it, add one teaspoonful of baking soda
to one quart of milk and immerse in it a strip of unglazed paper; in a
few hours examine the paper; if annatto is present, it will have
become an orange color.[5]

If the whole milk has a blue and thin appearance, or if the cream is
scant in quantity, it has probably been diluted with water. The
popular idea that chalk is sometimes added to poor milk to make it
appear of better quality is erroneous; chalk would always show as a
precipitate, as it does not dissolve, and the presence of such a
sediment would be a too obvious adulteration to be practiced.

Milk should always be kept at a temperature below 50 deg. F.; above that
temperature the bacteria in it multiply with great rapidity and render
it unfit for use.

Milk may be preserved for several days if "pasteurized" or
"sterilized." Pasteurization consists of heating milk to a temperature
of about 167 deg. F., and maintaining it at that degree for twenty
minutes. Sterilization means keeping the milk at a temperature of 212 deg.
F. for two hours and a half. Immediately after either process the milk
should be cooled, then placed in absolutely clean, covered bottles and
kept on ice. These methods are not only harmless but actually
beneficial in that they destroy any disease germs that might be
present.

Chemical preservatives are occasionally found in milk. They may be
suspected if the milk is alkaline in reaction and has a disguised
taste. The ones most commonly used are boric and salicylic acids and
formaldehyde; the two former can only be detected by chemical tests
too delicate and intricate to be used by the housewife. Formaldehyde
may be tested for by using a solution of one drop of a ten per cent
solution of ferric chloride to one ounce of hydrochloric acid.[6] Fill
a small porcelain dish one-third full of this solution; add an equal
volume of milk and heat slowly over a flame nearly to the boiling
point, giving the dish a rotary motion to break up the curd. If
formaldehyde is present, the mass will show a violet color, varying in
depth with the amount present; if it is absent, the mass turns brown.

=Butter.=--Good butter has a fresh, sweet odor and an agreeable taste.
It should be of the same color and consistency throughout, easily cut
and