Chemical lecture experiments . influenceof sunlight may be readily shown byfilling a 2 1. flask containing greenleaves (not too closely packed), withwater through which carbon dioxidehas been allowed to bubble (Fig. 4).A large funnel is passed through a holein the cork, which is firmly presseddown into the flask in such a mannerthat the carbon dioxide water will rise,thereby expelling the air in the stemof the funnel. The funnel is two-thirds filled with water, and a small cyl-inder filled with water is inverted withits mouth directly over the stem of thefunnel. The whole apparatus is placedin
Chemical lecture experiments . influenceof sunlight may be readily shown byfilling a 2 1. flask containing greenleaves (not too closely packed), withwater through which carbon dioxidehas been allowed to bubble (Fig. 4).A large funnel is passed through a holein the cork, which is firmly presseddown into the flask in such a mannerthat the carbon dioxide water will rise,thereby expelling the air in the stemof the funnel. The funnel is two-thirds filled with water, and a small cyl-inder filled with water is inverted withits mouth directly over the stem of thefunnel. The whole apparatus is placedin bright sunlight, and in a few hourssufficient oxygen will have risen and dis-placed the water in the small cylinder togive a good test. The apparatus may beleft, and the oxygen tested at the nextexercise. If the carbon dioxide water isnot too strongly charged with the gas, it will be unneces-sary to remove the trace of the carbon dioxide from theoxygen before testing. Apparatus (Fig. 4) ; green leaves ; carbon dioxide Fig. 4 7. From the electrolysis of copper sulphate. — In the elec-trolysis of copper sulphate, where but one of the finalproducts of electrical decomposition is gaseous, that product,oxygen, may be isolated and tested. (Compare with theelectrical decomposition of water, sodium sulphate solution,etc., where two gaseous products are formed.) 14 CHEMTCAL LECTURE EXPERIMENTS <- p The glass bottle of the electrolytic apparatus (Fig. 5) iscompletely filled with a saturated solution of copper sul-phate, and the cork insertedin such a manner as to driveout all the air and fill the de-livery-tube with the a current from four cells ofa bichromate battery is passedthrough the apparatus, a steadystream of oxygen will be de-livered. One of the platinumelectrodes, the negative one, will become coated almost in-stantly with metallic copper; the other, from which thebubbles of gas rise, will retain its original color. Pieces of cardboard with the signs +
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