The Romance of Modern Chemistry

CHEMISTRY AND AGRICULTURE bustible matter. In the combustible part there are to be found five chemical elements, namely, carbon, hydrogen, oxygen, nitrogen, and sulphur, the first three of which are present in by far the largest proportion. These three, combined in a variety of ways, constitute the woody matter or cellulose, the sugar, the starch, and the fats of the plant. Other ingredients of the combustible part of the plant are (1) the nitrogenous bodies, which contain nitrogen as well as carbon, hydro- gen, and oxygen, and (2) the albuminoids, in which sulphur is found as well as the other four elements. In the incombustible ash of the plant there are also five elements found, namely, potassium, magnesium, calcium, iron, and phosphorus; these are essential to the life of the plant, and exist in its tissues largely as carbonates, sulphates, and phosphates. These con- stituents, as well as some others which often occur but are not essential, are derived from the soil in which the plant grows, so that the nature and composition of the soil are all-important factors in the vitality of the plant. In order that the reader may get an idea of the relative proportions of the water, the ash, and the combustible matter in such a common vegetable product as meadow grass, the following figures are quoted. The crop to which the figures refer weighed 5 tons when freshly cut, and produced tons of hay. Out of the 5 tons—that is, 11,200 pounds—of meadow grass, 8378 pounds were water, while the combustible matter weighed 2613 pounds, and the ash 209 pounds. We have discussed the marvellous way in which the living plant procures its carbon, but the origin of some of the other constituents is also full of interest. Let us consider first the nitrogen, which, although it is present 220