Gas and petroleum engines; a practical treatise on the internal combustion engine - Softcover

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1890 Excerpt: ... them, or within infinitesimally small distance, but not till Laws of Chemical Combination. 323 then. In this respect chemical action is unlike gravity, which acts at a distance. A group or little system of atoms forms a molecule, which is the smallest quantity of an element or a compound that can exist in the free state. Molecules are far too small to be seen, and have never been isolated. Sir William Thomson has estimated that if a rain-drop were magnified to the size of the earth, each constituent molecule thus magnified would be larger than a single grain of small shot, but smaller than a cricket-ball. We must bear in mind that these molecules may be only a conception of the imagination of the modern scientist; still they enable him to form a good idea of what is going on inside a mass of matter, and to give a satisfactory explanation of experimental facts. It has been proved that a molecule of most of the simple gases consists of two atoms, whilst there may be a great number of atoms in the molecule of a compound. The fundamental law of chemical combination is that all compounds are constant in composition; in other words, the molecule of any substance has always the same atoms similarly arranged. Every molecule of pure water always consists of one atom of oxygen combined with two atoms of hydrogen, and is therefore indicated by the symbol H20. The number of hydrogen atoms is shown by the figure placed below the letter to the right, whilst a number at the beginning of the formula would tell the number of molecules. These letters also tell the weight as well as nature of the substance. H20 means 18 parts by weight of the compound water, containing 2 atoms or two parts by weight of H and 1 atom or 16 parts by weight of oxygen. The molecular weight of a c...