The Elements of Chemistry

a few facts, to get a clearer conception of what is actually meant by a chemical element. Action of Sodium and Potassium in Water. If a piece of the metal sodium is placed in contact with water, an instantaneous change takes place; the sodium becomes hot, it melts, and the globule of metal will move rapidly round on the surface of the water, t If the water is thickened with starch paste so that this movement cannot take place, the heat developed will finally produce a flame which is caused by the burning of a gas which is passing off. That such a gas is really liberated is easily proved by placing the piece of sodium in a wire net, and inverting over this a tube closed at one end, and filled completely with water. The gas will rise in bubbles, and, if the original quantity of the sodium was sufficient, will entirely fill the tube. If the latter is now removed, mouth downward, and held over a flame, the gas will take fire, and burn up completely when the tube is inverted. Essentially similar phenomena will be observed if the metal potassium is substituted for sodium, except that the change is much more violent. The gas bursts into flame even when the water has not been previously thickened with starch paste. The color of the flame with sodium is yellow, with potassium bluish-violet; and to a superficial observer it might appear that the gas given off by potassium and water is different from that produced by sodium and water. That this is not the case, however, ...