th the reagent by
means of a funnel. The tip of the burette is allowed to fill before the
readings are made, which are from the lowest point or meniscus. When
reagents are removed from bottles, the stopper should be held between
the first and second fingers of the right hand (see Fig. 75). Hold the
test tube or receptacle that is to receive the reagent in the left hand.
Pour the liquid slowly until the desired amount is secured. Before
inserting the stopper, touch it to the neck of the bottle to catch the
few drops on the edge, thus preventing their streaking down the sides of
the bottle on to the shelf. Replace the bottle in its proper place.
Every precaution should be taken to prevent contamination of reagents.

[Illustration: FIG. 76.--MICROSCOPE AND ACCESSORIES.

1, eye-piece or ocular; 2, objective; 3, stage; 4, cover glass; 5,
slide; 6, mirror.]

Use of the Microscope.--Special directions in the use of the
microscope will be given by the instructor. The object or material to be
examined is placed on a microscopical slide. Care should be exercised to
secure a representative sample, and to properly distribute the substance
on the slide. If a pulverized material is to be examined, use but little
and spread it in as thin a layer as possible. If a liquid, one or two
drops placed on the slide will suffice. The material on the slide is
covered with a cover glass, before it is placed on the stage of the
microscope. In focusing, do not allow the object glass of the microscope
to come in contact with the cover glass. Focus upward, not downward.
Special care should be exercised in focusing and in handling the
eye-piece and objective. A camel's-hair brush, clean dry chamois skin,
or clean silk only should be used in polishing the lenses. Always put
the microscope back in its case after using.

Experiment No. 1

Water in Flour

Carefully weigh a porcelain or aluminum dish. (Porcelain must be used if
the ash is to be determined on the same sample.) Place in it about 2 gm.
of flour; record the weight; then place the dish in the water oven for
at least 6 hours. After drying, weigh again, and from the loss of weight
calculate the per cent of water in the flour. (Weight of flour and dish
before drying minus weight of flour and dish after drying equals weight
of water lost. Weight of water divided by weight of flour taken,
multiplied by 100, equals the per cent of water in the flour.)

How does the amount of water you obta