Element Boron, B, Metalloid. Among the non-metallic elements, boron. Containing carbon, and obtained from the two elements at a very high temperature, is of a similar character, and also possesses an adamantine hardness. This also ought most probably to be regarded as a solid solution, and not as a chemical compound. The combining weight of boron is B. Have been known of for thousands of years. Century a substance was disengaged from burah. Which was called boronic acid. And Davy called it boron.

Element Lead, Pb, Poor Metal. Calcium, which exhibits relations of isomorphism in both directions, stands in the middle. On the other hand, lead is decidedly a heavy metal, and forms an insoluble, dark-coloured sulphur compound. The combining weight of lead has been determined by the conversion of the metal into the oxide, and vice versa. It has been found to be Pb. Greeks called it molybdos; the same n.

Element Nitrogen, N, Non Metal. There is present in the air, besides oxygen, another substance which constitutes the greater part both by weight and by volume. From the fact that the residue of the air after removal of the oxygen can support neither combustion nor life, it was called azote, but it is now called nitrogen. Its chemical symbol is N. Its combining weight is N. Is in so far of especia.

Element Phosphorus, P, Non Metal. The name phosphorescence, used in physics for the after luminescence shown by certain substances after a previous exposure to light, is a relic of that usage. At the present day, the name phosphorus. The nerve and brain substances, more especially, are comparatively rich in phosphorus, which is there .

Element Silicon, Si, Metalloid. Silicon stands to carbon in the same relation as sulphur to oxygen. The two elements are similar in many respects, but differ more from one another than, for example, chlorine, bromine, and iodine do. Like carbon, occurs in several forms, of which an amorphous and a crystalline form are accurately known. Amorphous silicon is obtained by conducting its chlorine or fluorine compound over heated potassium; the metal unites with the halogen, and the silicon.

Element Aluminium, Al, Poor Metal. Of all the light metals, aluminium. It forms a constituent of almost all crystalline silicate rocks; and of the secondary formations, the clays and slate formations are formed from aluminium silicate. A knowledge of the compounds of this metal, therefore, extends back as far as chemical knowledge at all can be traced. While, even at comparatively high temperatures, massive aluminium is only superficially and inappre.