Volume 2

The elements of experimental chemistry / by William Henry.

  • Henry, William, 1774-1836.
Date:
1815
Catalogue details

Licence: Public Domain Mark

Credit: The elements of experimental chemistry / by William Henry. Source: Wellcome Collection.

Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.

    133/586 (page 115)
    (a) Write upon paper with an infusion of galls. The oharactcrB will not be legible till a solution of sulphate of iron is applied. This experiment may be reversed like the prcceding^ one (V. f). {li) The combination of iron, forming ink, is destroyed by pure and carbonated alkalis. Apply a solution of alkali to characters written with common ink, the blackness will dis- appear, and the characters will become brown, an oxide of iron only remaining on the paper. AlkaliS) added cautiously to liquid ink, precipitate the black combination, but an excess re-dissolves the precipitate^ (c) Characters, which have been thus defaced^ may again be rendered legible by an infusion of galls. (cf) Ink is decomposed by most acids, which separate the oxide of iron from the gallic acid in consequence of a stronger affinity. Hence ink stains are removed by dilute muriatic acid, and by some vegetable acids. Hence, also, if to a sa- turated solution of sulphate of iron there be added an excess of acid, the precipitate no longer appears on adding infusion of galls. When a mixture of ink is heated with nitric acid, the yellow oxalate of iron is formed, and is precipitated on adding pure ammonia. {e) Ink is decomposed by age, partly in consequence of the farther oxydation of the iron, and partly, perhaps, in consequence of the destruction of the acid of galls. Hence ink-stains degenerate into iron-moulds, and these last are immediately produced on an inked spot of linen when washed with soap, because the alkali of the soap abstracts the gallic acid, and leaves only an oxide of iron. U ) is decomposed by oxy-muriatic acid, which de- stroys the gallic acid, and the resulting muriatic acid dissolves the oxide of iron. As all writing inks, into the composition of which iron enters, are liable to decay by time, and to be destroyed by various agents, an ink has been proposed by Mr. Close, the basis of which is similar to that of printing ink.—Take oil of lavender 200 grains, gnm copal, in powder, 25 grains, and J 2