They comprise the gases—oxygen, hydrogen, nitrogen, and chlorine, and such substances as sulphur, carbon, phosphorus and iodine. To the latter class also belongs a peculiar element called fluorine, which, when combined with hydrogen, destroys glass. It is the only liquid known which cannot be contained in a glassen or earthenware vessel, and when used for experimental purposes must be kept in a leaden bottle.
Of course it will be understood that the above is not a complete list by any means, but is sufficient to give a clear idea of the difference between the two classes. The metals generally speaking are of a more or less sparkling, lustrous appearance. The metals, too, are good conductors of heat and electricity, and generally heavy. These characteristics are almost entirely wanting in the non-metals. We shall now give some tricks with the metals.
Potassium.
Potassium was discovered by Sir H. Davy, in the beginning of the present century, while acting upon potash with the enormous galvanic battery of the Royal Institution, consisting of two thousand pairs of four inch plates. It is a brilliant metal, so soft as to be easily cut with a penknife, and so light as to swim upon water, on which it acts with great energy, uniting with the oxygen and liberating the hydrogen, which takes fire as it escapes.
Trace some continuous lines on paper with a camel’s-hair brush dipped in water, and place a piece of potassium about the size of a pea on one of the lines, and it will follow the course of the pencil, taking fire as it runs, and burning with a purplish light.
The paper will be found covered with a solution of ordinary potash. If turmeric paper be used, the course of the potassium will be marked with a deep brown color. Hence if you touch potassium with wet fingers you will burn them.
If a small piece of the metal be placed on a piece of ice, it will instantly take fire, and form a deep hole which will be found to contain a solution of potash.
In consequence of its great affinity for oxygen, potassium must be kept in some fluid destitute of it, such as naphtha acid, which has been displaced by the great affinity or liking of the oxygen and acid for the copper.