ELEMENTS, CHEMICAL. The word elements has a very different signification in modern science from what it once had. The earliest of the Greek philosophers assumed either a single element, or several, the modifications and combinations of which they held to give rise to all the things that we see. The most common assumption was that of four elements —fire, air, water, and earth. This corresponds to the four forri\s under which modern science considers matter as existing—viz., imponderable, gaseous, liquid, and solid; while by elements are understood the simple component ingredients of bodies under whatever form they exist. Neither air, water, nor earth are elements in this sense, for they can be decomposed into simpler ingredients, and fire is a combination of light and heat. It is not pretended that any of the substances called elements are absolutely simple, that is, contain only one kind of matter; but only that hitherto they have not been decomposed. The num ber of so-called simple bodies, or elements, recognized by chemists is 64, of which some have been known from ancient times, such as the metals gold, silver, lead, copper, tin, and mercury; others are of more recent date; whilst quite lately two new metallic elements have been added to the list—viz., ciesium and rubidium, both of which were discovered by prof. Bunsen of Heidelberg, by the aid of the new branch of practical chemistry named spectrum analysis. The elements are divided into two great classes—the non-metals and metals. The latter are the more numerous class, there being altogether 51, whilst the non-metals number only 13. The following table gives the names of the elements at present known: Univ Calif - Diaitizea bY Microsoft The more rare elements are printed in italics. Although the classification adopted above
is a convenient one for the study of the elements, yet there is no decided line of demarka tion between the metallic and non-metallic (otherwise called metalloid) series. The metals are generally; recognized (1) by their power of reflecting light, as exhibited in the luster of burnishedgold, and even in ordinary mirrors, which owe their power of reflecting light to the amalgam of the metals mercury and tin, present on the glass; (2) by their power of conducting heat; and (3) by their ready transmission of electricity. The non metals or metalloids are regarded as not possessing all these three attributes. The non metals carbon and silicon, however, in certain forms conduct electricity, whilst the metals arsenic and tellurium very closely resemble the metalloids in many of their properties. In the combinations of the various elements with each other, the non-metals constitute the electronegative ingredient, and, as a rule, are insulators in the galvanic current; whilst the metals form the electropositive element of the combination, and are conductors of the electric fluid. Again, in their combination with oxygen, the non metals form more or less powerful acids, whilst the metals produce more or less powerful bases. At ordinary temperatures, five of the E. are gaseous—viz., oxygen, hydrogen, nitrogen, chlorine, and fluorine; two are liquid—viz., bromine and mercury; whilst the remaining 57 are solid.