A practical treatise on the use and application of chemical tests. With concise directions for analyzing metallic ores, earths, metals, soils, manures, and mineral waters. Illustrated by experiments / By Fredrick Accum.

  • Accum, Friedrich Christian, 1769-1838.
Date:
1820
Catalogue details

Licence: Public Domain Mark

Credit: A practical treatise on the use and application of chemical tests. With concise directions for analyzing metallic ores, earths, metals, soils, manures, and mineral waters. Illustrated by experiments / By Fredrick Accum. Source: Wellcome Collection.

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    EXPERIMENT XIII. Dip a piece of litmus paper into water strongly impregnated with sulphuretted hy- drogen gas: its blue colour will gradually be changed to a faint red; dry the paper, _ and its original colour will re-appear. Paper stained with the juice of the violet flower, or the scrapings of purple radishes, answers the same purpose. | The colour of litmus paper ought to be a pale, not dark, violet blue. ‘This paper, when long kept exposed to the contact of air and light, loses its colour, and then becomes unfit for use. It should therefore be pre- served in opake stopped bottles, or placed between the leaves of a book. Litmus paper is readily prepared, by dipping fine writing paper into tincture of litmus, and suffering it to dry slowly. The paper employed should first be freed from the portion of glue, alum, and other foreign matters, which all writing paper contains, dA