wder or precipitate in a silver nitrate solution
by adding hydrochloric acid (page 327), is a regular chemical test
to find out whether or not a thing has silver in it. If any silver
is dissolved in nitric acid, you will get a precipitate (powder) when
hydrochloric acid is added. Make the test in the following experiment:

EXPERIMENT 114. _Use distilled water all through this
experiment if possible._ First wash two test tubes and an
evaporating dish thoroughly, rinsing them several times. Into
one test tube pour some nitric acid diluted 1 to 4. Heat this
to boiling, then add a few drops of hydrochloric acid diluted
1 to 10. Does anything happen? Pour out this acid and rinse
the dish thoroughly. Now put a piece of silver or anything
partly made of silver into the bottom of the evaporating dish.
Do not use anything for the appearance of which you care.
Cover the silver with some of the dilute nitric acid, put the
dish over the Bunsen burner on a wire gauze, and bring the
acid to a gentle boil. As soon as it boils, take the dish off,
pour some clean, cold water into it to stop the action, and
pour the liquid off into the clean test tube. Add a few drops
of the dilute hydrochloric acid to the liquid in the test
tube. What happens? What does this show must have been in the
liquid?

You can detect very small amounts of silver in a liquid by this test.
It is a regular test in chemical analysis.

THE IODINE TEST FOR STARCH. A very simple test for starch, but one
that is thoroughly reliable, is the following:

EXPERIMENT 115. Mix a little starch with water. Add a drop of
iodine. What color does the starch turn? Repeat with sugar.
You can tell what foods have starch in them by testing them
with iodine. If they turn black, blue, or purple instead of
brown, you may be sure there is starch in them. And if they do
not turn black, blue, or purple, you can be equally sure
that they have no starch in them. Some baking powders contain
starch to keep them dry. Test the baking powder in the
laboratory for starch. Often a little cornstarch is mixed
with powdered sugar to keep it from lumping. Test the powdered
sugar in the laboratory to see if it contains starch.

Test the following or any other ten foods to see if any of
them are partly made of starch: salt, potatoes, milk, meat,
sausage, butter, eggs, rice, oa