Inorganic chemistry / by Edward Frankland and Francis R. Japp.

  • Edward Frankland
Date:
1884
Catalogue details

Licence: Public Domain Mark

Credit: Inorganic chemistry / by Edward Frankland and Francis R. Japp. Source: Wellcome Collection.

    29/856 (page 3)
    and heavy metal iron, could not even be suspected in the dull, soft, brown, and comparatively light rust, into which it is converted by exposure to the air; still less, perhaps, could the rust be credited with the presence of the colourless and invisible gas, oxygen, which is held in combination with the iron by chemical energy. The change is such as is not produced1 by mixture only. Mechanical mixture, however intimate, does not conceal the properties of iron and sulphur, for instance. The magnetic quality of the iron is as marked as ever, and the two constituents may be distinguished and even separated from each other under the microscope. But after these substances have been subjected to chemical action, the most powerful microscope is incompetent to detect either sulphur or iron, and the magnetic property of the metal almost entirely disappears. This change of properties is manifested in various ways: sometimes liquids or gases are converted into solids, or vice versd, sometimes a change in colour, taste, odour, or medicinal pro- perties is produced, and there is always a change of temperature, sometimes in the direction of heat, and sometimes in that of cold. With all these changes, however, there is never the slightest altera- tion in the weight of the materials operated upon. In the second place, chemical affinity cannot act through an appreciable intervening space. Heat, light, and electricity affect bodies at considerable distances, whilst gravity acts through spaces inconceivably great; but if two substances, between which the chemical force is energetically exerted when they are in contact, be placed at the smallest appreciable distance from each other, no chemical action whatever occurs, even after they have been in closo proximity for years. Of all other forces, cohesion alone requires this intimate contact. If two pieces of plate glass be gently placed one upon the other, the slightest effort suffices to separate them, but if they be pressed together, they markedly cohere, and if strongly pressed for a long time, they can no longer be separated. The two pieces have become one by cohesion, but the properties of the glass are unaltered, and cohesive action is thus sharply distin- guished from chemical action. The most distinguishing characteristic of the chemical force, however, is the limitation of its action to fixed and definite quanti- ties of matter. Each chemical compound not only always contains the same kinds of matter, but its constituents are always present in exactly the same proportions, although the specimens of the compound may have been derived from the most widely different B 2