.10
1 thistle tube .10
Covered wire, copper .10

CHEMICALS

Iodine crystals .10
Sulphuric acid, 1 lb. .10
Methylated spirits 1 pt. .20
Alcohol, 95% .10
Mercury, 1/2 lb. .50
Pot. chlorate .15
Manganese dioxide .10

The following may be obtained, for either list, at little or no cost
from household stores or home-made sources: washing soda, sugar, salt,
ammonia, coal, coke, saltpetre, sulphur, blue vitriol, alum, potass.
bichromate, blueing, lime, pickle-jars, wire gauze, candles, wire, sheet
metals, test-tube holder and rack, balance, battery cells, horse-shoe
magnet, pneumatic trough, lamp chimneys, tin cans, melting spoon,
bicycle pump, baking-powder.

For home-made apparatus, consult _Laboratory Exercises in Physics_ by
Newman, Ginn & Co., 50c., and Manual on _Manual Training_.

Reference has been made in the preceding experiments to the use of
simple and easily contrived apparatus. The more of this the pupils can
contrive and make under the direction of the teacher, the more valuable
will be the course in Physical Science.

GRENET CELLS

Into a pint gem-jar put water 10 parts, sulphuric acid 1 part, potass,
bichromate 1 part. Have jar three quarters full. Cut a piece of board 4
in. square, bore two holes in it, and through the holes thrust two
pieces of electric light carbon, 5 in. or 6 in. long. The outer edges of
the carbons should not be more than two inches apart. With a saw, cut a
slit in the board between the holes and insert a strip of zinc 2 in. by
7 in. previously rubbed over with mercury. Set the three elements in the
jar, connect the two carbons to one wire, and the zinc to another.

One cell of this kind will run a small motor, operate a telegraph
sounder, make a simple electro-magnet, or ring an electric bell; two
cells will decompose water: three will heat a piece of fine iron wire
red-hot.

DECOMPOSITION APPARATUS

1. Cut the neck end from a pickle bottle. Get a No. 1 stopper, (rubber)
with two holes in it and insert a piece of