Elements of chemistry, in two volumes / by John Murray.

  • Murray, John.
Date:
1828
Catalogue details

Licence: Public Domain Mark

Credit: Elements of chemistry, in two volumes / by John Murray. Source: Wellcome Collection.

    139/768 (page 127)
    > i2r form, give rise to an invariable proportion. The opinion of Berthollet is now generally abandoned: indeed, the cases are so numerous of metals which combine in well- marked and definite proportions, and the analogy of other chemical combinations in which the law of definite pro- portions is observed is so strong, that the common doc- trine is the only one that can be maintained. The sup- position of Proust is, however, too limited ; for there are many metals which form three, and some which form even four or five compounds with oxygen. Those oxidated products which, on Berthollet’s view, were regarded as distinct oxides, are now considered as intermixtures of a few oxides of definite constitution. The nomenclature by which the different oxides of each metal are denominated, is one extremely convenient, which was proposed by Dr Thomson. It is that of pre- fixing the Greek numerals to denote the degree of oxida- tion. Thus, an oxide which consists of one equivalent of the metal and one of oxygen, is termed the protoxide; that in which there are two equivalents of oxygen, the deutoxide ; that in which there are three, the tritoxide or teroxide; and the oxide which contains the highest pro- portion of oxygen, the peroxide. Where there is only one compound it may be called simply the oxide. When, as in a few cases happens, two equivalents of metals are united with one of oxygen, the name of suboxide is given to the compound. In those instances where the metal acquires by oxidation acid powers, the name of the acid is simply derived from the metal: thus we have the Chro- mic and Arsenic acids. Oxides are frequently also dis- tinguished by their colour: thus we have the black and red oxides of iron. The following table exhibits the com- position of most of the metallic oxides :