A text-book of inorganic chemistry / by Dr. A.F. Holleman ... Issued in English in coöperation with Hermon Charles Cooper.

  • Arnold F. Holleman
Date:
1912
Catalogue details

Licence: In copyright

Credit: A text-book of inorganic chemistry / by Dr. A.F. Holleman ... Issued in English in coöperation with Hermon Charles Cooper. Source: Wellcome Collection.

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    must be somewhere a limit to the divisibility and that we must finally arrive at particles incapable of fuither division, the atoms. In the filth century n,c. there existed a school of philosophy, that of the Elcatics (so called from the city of Elea), whose most prominent representative was Paumenides. He taught tliat everything that exists cannot be otherwise conceived than as unchangeable; trans- formation of the existent, which was thought to hav'e never originated and to be at the same time unalterable, was held by them to be incon- ceivable. These theses they regarded in a certain sense as axioms, i.c. statements of truths which are accepted without ])roof. Daily experience tea(;hes one nevertheless that transformation does occur in that which exists, a fact that led them to suppose that everything observed by men is merely appearance. 'riii'ee theoi-ies were i)roposed in the same century which aim to form a bridge between the docdrinc of the unalterable existent and the experience that points towaid continuous change. These theories originated with Empedocles, Axaxagokas, and the AlomisLs, Leccippus and Democrites. The immutability of the existent is disposed of by ascribing it to extremely small unchangeable and indestructible particles; every change is thought to depend on the movement of these smallest integral particles toward oi’ away from each other. Empedoclf.g and Anaxagoras assume in this connection an infinite divisibility; the Atomists, on the contrary, regard the world as built up of indivisible particles, atoms, all of which consist of the same primordial substance but differ in form and size. Now Dalton has used this conception of the ancients regarding the atom to ex[)lain the fact that the combining weights are con- stant. The atoms of the various elements, he assumes, have dif- ferent weights; the atoms of the sa?ne element are alike in weight. A compound of two elements is therefore jiroduced by the associa- tion of atoms of these elements. Such a combination of two or more atoms is called a molsculs. It is obvious that these suj^posi- tions lead directly to the Imo of constant propoiiions; for, if copper oxide is formed by an atom of copper uniting with an atom of oxygen to make a molecule of copper oxide, its composition must, according to the above hypothesis, be constant. Dalton deduced another conclusion from his hypothesis, and confirmed the same experimentally. lie observed that oxygen unites not only with one very definite amount of nitrogen oxide, but also with twice as much, not, however, with any intermediate