. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. 18 BOTANY ^ h time. This will occur before all the wood is consumed. Another splinter of wood, placed in a jar with the cover off, will burn slowly but completely. A third piece of wood burned in the air will be quickly and completely consumed. If now a little limewater^ is poured into the jar which was closed, and the contents shaken up, the limewater will be found to turn a milky color. This milky appearance is due to the formation within the jar of a material known as calcium carbonate.
. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. 18 BOTANY ^ h time. This will occur before all the wood is consumed. Another splinter of wood, placed in a jar with the cover off, will burn slowly but completely. A third piece of wood burned in the air will be quickly and completely consumed. If now a little limewater^ is poured into the jar which was closed, and the contents shaken up, the limewater will be found to turn a milky color. This milky appearance is due to the formation within the jar of a material known as calcium carbonate. This is thrown down in the liquid as a result of the union of carbon with lime. Evidently some of the carbon from the wood has passed in the form of a gas into the limewater and there united with the calcium in the lime. Remembering what we know about oxidation, we see that the carbon of the wood has passed ofif and united with oxygen of the air in the jar. Thus, by the uniting of the two chemical elements, a chemical compound has heenformed. The presence of carbon dioxide is known by the fact that it puts out a flame and that it turns limewater milky. This compound is known to chemists as carbon dioxide.^ Nitrogen. — There is another gaseous substance that will not support combus- tion; this is the element nitrogen. Its presence in the atmosphere is shown by the following experiment: — Invert a bell jar in a large, deep dish of water, having previously placed within the jar on the surface of the water a piece of phosphorus sup- ported on a flat bit of wood or cork. Leave the experiment for at least two days undisturbed (or, the phosphorus may be lighted and then the jar left for a few hours untouched). After that time the water will be found to have risen considerably in the jar.^ If you make a mark on the cover * Limewater can be made by shaking up a piece of quicklime the size of your fist in about two quarts of water. Filter or strain the limewater into bottles and it i
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