2. A piece of picture wire tipped with sulphur burns with great brightness.
3. Burn phosphorus or match heads in a spoon. A spoon may be made by attaching to a wire a bit of crayon having a hollow scooped on its upper surface. A clay pipe bowl attached to a wire will answer.
From these experiments pupils will learn the value of nitrogen as a diluent of the oxygen. Pure oxygen entering the lungs would be just as destructive as it would be entering the furnace.
CARBON DIOXIDE
1. Make a jar of this gas. Washing soda and vinegar will answer if hydrochloric acid and marble are not obtainable. (Consult the Science of Common Life, Chap. XIII, and any Chemistry text-book.)
2. Lower a lighted candle first into a jar of air then into the jar of carbon dioxide.
3. Make some lime-water by stirring slaked lime with water and allowing the mixture to settle. Shake up some clear lime-water with a jar of the gas. Pupils will be made to understand that the milky colour will in future be considered the test for carbon dioxide.
4. Have one of the pupils cause his breath to bubble through some clear lime-water for a minute. Using a bicycle pump, cause some fresh air to bubble through lime-water.
5. Hold a clear jar inverted over the candle flame for a few seconds, then test with lime-water.
6. Invert a large jar over a leafy plant for a day. Keep in the dark and test the jar with lime-water.