FLUIDS AND SOLUTIONS.

_21. Sulphuric Acid._ THIS ACID MUST BE HANDLED WITH GREAT CARE, as it
(the concentrated) is very strong, and will burn the hands, eat holes in
clothing, carpets, etc.; it will even char wood. Do not let any of it
drop anywhere accidentally. If you wish to pour concentrated acid into a
bottle, place the bottle to be filled upon a plate, and wipe all drops
of acid from the outside of it afterward. The concentrated acid should
be kept in tightly-corked bottles, as it absorbs moisture from the air
very rapidly. Ordinary corks should be paraffined if they are to be used
in acid bottles, or they will be soon eaten up.

22. Mixing. When sulphuric acid and water are mixed, considerable heat
is produced. Never pour water into the acid, as the heat would be
produced so rapidly that the vessel containing the mixture might break.
Always pour the acid into the water, and thoroughly stir the mixture at
the same time. Earthen vessels do not break when heated as easily as
glass ones. The mixing may be done in ordinary glass fruit-jars, if care
be taken to pour the acid slowly into the water. The jars should be set
in some larger dish, or in the sink, before adding the acid. If they get
too hot, allow them to cool a little before proceeding with the mixing.
As the acid is much heavier than water, it will immediately sink to the
bottom of the jar, unless constantly stirred.

23. There are different grades of acid upon the market. For battery
purposes you do not need the chemically pure (C P) acid. The ordinary
"commercial acid" is all right, even though it is a little dark in
color. You can get this at any drug-store. Get 5 or 10 cents' worth at a
time.

APPARATUS 14.

_24. Battery Fluid for Simple Cells._ For the simple cell (App. 5), when
it is to be used for experiments with detectors or in the study of
polarization, etc., a very dilute acid is best. Mix 1 fluid ounce of
commercial acid with 1 pint of water. This will make 17 fluid ounces
(See App. 19), and your mixture will be one-seventeenth acid. Make up a
pint or quart bottle of this at a time, and label it with the date:

Dilute sulphuric acid.
1 part acid, 16 parts water.
Apparatus 14.

25. Note. Do not fail to paste a label on all bottles as soon as you
have put anything into them. Give the date, contents, and any other
information that will help you to reproduce the mixture again. Do not
write on them any abbreviations or other things that