The evening times. [volume] (Grand Forks, N.D.) 1906-1914, 1906-07-28

vessel of warm water may, of course.
be omitted. Benzoic acid, II present
In considerable amount, will now APP
pear in the dish in characteristics
fiat crystals. On warming the dish
the unmistakable Irritating odor of
benzoic acid may be obtained. This
method will detect benzoic acid in
tomato catsup or other articles in
which it is used in large quantities.
1t is not sufficiently delicate, how
ever. for the smaller amount used
with some articles, such as wine 1t
is often convenient to extract
larger quantity of the sample and
divide the chloroform layer into two
portions. testing one for salicylic
acid and the other for benzoic acid.
Detectio. Of Boric Acid a.d Berax.
Boric acid (also called boracic acid)
and its compound with sodium dor
aX) are often used to preserve ami
NAL products, such as sausage, but
ter and sometimes milk. For the de-
lection of boric acid and borax,
solids should be macerated with a
small amount of water and strained
through white cotton cloth. The
liquid obtained by treating solids in
this manner is clarified somewhat by
thoroughly chilling and filtering
through filter paper.
In testing butter place a heaping
teaspoonful of the sample in a tea
cup, add couple of teaspoonfuls of
hot water. and stand the cup in
vessel containing little hot water
until the butter is thoroughly melted.
Mix the contents of the cup we'll by
stirring with teaspoon and set the
cup with the spoon in it in a cold
place until the butter is solid. The
spoon with the butter (which adheres
to it, is now removed from the cup
and the turbid liquid remaining
strained through white cotton cloth,
or better. through filter paper. The
liquid will not all pass through the
cloth or filter paper, but sufficient
amount for the test may be secured
readily.
In testing milk for boric acid two
or three tablespoonful of milk are
placed in a bottle with twice that
amount of solution of teaspoon
full of alum in pint of water, shaken
vigorously, and filtered through filter
paper. Here again clear or only
slightly turbid liquid passes through
the paper.
About teaspoonful of the liquid
obtained by any one of the methods
mentioned above is placed In any dish
not metal, and five drops of hydro
chloric (muriatic) acid added. A
strip OF turmeric paper Is now dipped
into the liquid and then held in a
warm place-near stove or lamp
till dry. If boric acid or borax was
In tha <,,r
paper becomes bright cherry red when
dry. A drop of household ammonia
changes the red color to dark green
or greenish black. II too much
hydrochloric acid is used the tur-
red color even in the absence of
boric acid. In this case, however, am
monia changes the color to brown
just as it does turmeric paper which
has not been dipped into the acid
solution.
Detection Of Formaldehyde.
Formaldehyde is the substance most
commonly used for preserving milk
and is rarely, If ever, added to any
other food. Its use is inexcusable and
especially Objectionable in milk
served to infants and invalids.
To detect formaldehyde in milk
three or four tablespoonsfuls of the
sample are placed in a teacup with
at least an equal amount of strong
hyrochloric acid and a piece of fer
ric alum about as large as pin
head, the liquids being mixed by a
gentle rotary motion. The cup is then
placed in vessel of boiling water
no further heat being applied, and
left for five minutes. At the end of
this time, if formaldehyde be present,
the mixture will be distinctly purple.
If too much heat is applied, muddy
appearance is impaired to the con-
tents of the cup.
Caution.-Great care must be ex-
ercised in working with hydrochloric
acid, as it is strongly corrosive. 1t
must not come in contact with the
flesh or clothes of the operator nor
with any metallic vessels and must
be greatly diluted with water before
it is poured into the sink.