rs wet with kerosene.) _Chlorine._ Pour strong hydrochloric acid on a
little manganese dioxide in a test tube, and warm gently over a low flame.
The escaping gas is chlorine. Avoid breathing much of it.

*Composition of the Nutrients.*--The simplest way of determining what
elements make up the different nutrients is by heating them and studying
the products of decomposition, as follows:

_To show that Carbohydrates contain Carbon, Hydrogen, and Oxygen._--Place
one half teaspoonful of powdered starch in a test tube and heat strongly.
Observe that _water_ condenses on the sides of the tube and that a black,
charred mass remains behind. The black mass consists mainly of _carbon_.
The water is composed of hydrogen and oxygen. These three elements are
thus shown to be present in the starch. The experiment may be repeated,
using sugar instead of starch.

_To show that Proteids contain Carbon, Hydrogen, Oxygen, Nitrogen, and
Sulphur._--Place in a test tube some finely divided proteid which has been
thoroughly dried (dried beef or the lean of hard cured bacon). Heat
strongly in the hood of a chemical laboratory or some other place where
the odors do not get into the room. First hold in the escaping gases a wet
strip of red litmus paper. This will be turned blue, showing _ammonia_
(NH3) to be escaping. Next hold in the mouth of the tube a strip of a
paper wet with a solution of lead nitrate. This is turned black or brown
on account of _hydrogen sulphide_(H2S) which is being driven off. Observe
also that _water_ condenses in the upper part of the tube and that a
black, charred mass remains behind. Since the products of decomposition
(H2O, NH3, H2S, and the charred mass) contain hydrogen, oxygen, nitrogen,
sulphur, and carbon, these elements are of course present in the proteid
tested.

_To show the Presence of Mineral Matter._--Burn a piece of dry bread by
holding it in a clear, hot flame, and observe the ash that is left behind.
This is the mineral matter present in the bread.

*Tests for Nutrients.* _Proteids._--Cover the substance to be tested with
strong nitric acid and heat gradually to boiling. If proteid is present it
turns yellow and partly dissolves in the acid, forming a yellow solution.
Let cool and then add ammonia. The yellow solid and the solution are
turned a deep orange color. Apply this test to foods containing proteid
such as white of egg, cheese, lean meat, etc.

_Starch._--_(a)_ Place a small lump of star