the sapphire, magnesia, lime, all entered into fusion. Fragments of diamond, and points of charcoal and plumbago, rapidly disappeared and seemed to evaporate in it, even when the was made in a receiver exhausted by the air pump ; but there was no evidence of their having previously under gone fusion. Copper and zinc are not the only metals proper for forming a galvanic battery, but they are the least expensive. The following tables by Sir II. Davy will furnish a variety of combinations. The metal first named is positive in reference to those that follow.
Ordinary Acids.
Potassium and its amalgams ; barium and its amalgams; amalgam of zinc; zinc ; amalgam of ammonium, cadmium, tin, iron, bismuth, antimony, lead, copper, silver, palladium, tellurium, gold, charcoal, platinum, iridium, rhodium.
Alkaline Solutions.
The metals of the alkali, and their amalgams, zinc, tin, lead, copper, iron, silver, palladium, gold, platinum, &c.
With the Solutions of Hydro-Sulpkurets.
Arrangements consisting of one Conductor and two Imperfect Conductors.
The most splendid effects of the voltaic baftery achieved by Sir H. Davy were the decomposition of the alkalies and alkaline earths, as potash, soda, baryta, strontia, lime, and magnesia. These were found to be composed of a brilliant white metal combined with oxygen, which were separated and exhibited at the opposite poles of the battery. This mode of decomposition, arising from electric repulsion, has afforded a convenient basis for the arrangement of the simple substances for the convenience of study, and by its means they are divided into two classes. The first consists of those elements which are attracted from their compounds with substances of the other class, by the positive pole of the voltaic pile; and as bodies in opposite states of electricity attract one another, they have been called electro-negative bodies. The second comprises those elements that are attracted by the negative pole, which are therefore termed electro-positive bodies. Before giving a list of the simple substances, it will be necessary to
allude to the theory of equivalents. In an early part of this article we have stated that different bodies combine in proportions that are fixed with regard to each other in a given compound. We may now observe that these proportions are definite with regard to every other substance with which they are capable of entering into composition, so that there are certain determinate proportions of all bodies which are equivalent to each other in their powers of combining with all other bodies. Thus, acetate of lead is a compound of'50 parts of acetic acid and 112 parts of lead, in the state of an oxide. White vitriol, or sulphate of zinc, is composed of 40 parts of sulphuric acid and 41 parts of oxide of zinc. Now these proportions are all equivalent to one another, and if the numbers are written against the different substances as follows, we can at once perceive the proportions in which they will unite in any new combination.
The same equivalent numbers or their multiples are preserved in every possible combination with other bodies ; and when any body is compounded of two simple substances, the sum of the equivalents of the two elements will give the number, denoting the proportion in which it will combine. Thus the prime equivalent of hydrogen is I, that of oxygen 8; these combine to form water, the equivalent of which is 9. The following table contains the names of those substances which being, in the present state of chemistry, undecomposable, are considered as simple elementary bodies, classed in two divisions, and having their equivalent or combining numbers attached.
A particular description of the properties of these bodies, with the compounds formed by their union with h other, will be found under the initial letter of their respective names.