The decomposition of the fixed alkalies and alkaline earths / H. Davy.

  • Davy, Humphry, Sir, 1778-1829.
Date:
1902
Catalogue details

Licence: In copyright

Credit: The decomposition of the fixed alkalies and alkaline earths / H. Davy. Source: Wellcome Collection.

    15/60 (page 11)
    I soon found to be pure potash, which immediately deliquesced, and new quantities were formed, which in their turn attracted moisture from the atmosphere till the whole globule disappeared, and assumed the form of a saturated solution of potash.* When globules were placed in appropriate tubes con- taining common air or oxygene gas confined by mercury, an absorption of oxygene took place; a crust of alkali instantly formed upon the globule ; but from the want of moisture for its solution, the process stopped, the interior being defended from the action of the gas. With the substance from soda, the appearances and effects were analogous. When the substances were strongly heated, confined in given portions of oxygene, a rapid combustion with a bril- liant white flame was produced, and the metallic globules were found converted into a white and solid mass, which in the case of the substance from potash was found to be potash, and in the case of that from soda, soda. Oxygene gas was absorbed in this operation, and nothing emitted which affected the purity of the residual air. The alkalies produced were apparently dry, or at least contained no more moisture than might well be conceived to exist in the oxygene gas absorbed; and their weights considerably exceeded those of the combustible matters consumed. * Water likewise is decomposed in the process. We shall here- after see that the bases of the fixed alkalies act upon this substance uith greater energy than any other known bodies. The minute theory of the oxydation of the bases of the alkalies in the free air, is this:—oxygene gas is first attracted by them, and alkali formed. This alkali speedily absorbs water. This w’ater is again decomposed. Hence, during the conversion of a globule into alkaline solution, there is a constant and rapid disengagement of small quantities of gas.