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 platinum foil 2 in. by 1/8 in. into each hole so that 1/2 in. projects above and below. Insert a tight plug beside each strip, thus holding it fast and making the stopper watertight. Insert the stopper into the neck of the jar. Pour into the vessel thus formed enough water to cover the platinums, and add a few drops of sulphuric acid. Touch the wires from the battery to the lower ends of the strips. Note bubbles of gas arise from the platinums. These may be collected in test-tubes and found by test to be oxygen and hydrogen.
2. Fasten a strip of platinum 1 in. by 1/8 in. to each wire from the battery and dip these into some acidulated water contained in a tumbler. The decomposition of the water into two gases can be seen, but the gases cannot be collected so readily as in 1 above. Bits of electric light carbon will do instead of platinum if the current is not too weak.