A manual on dental metallurgy / by Ernest A. Smith.

  • Smith, Ernest A. (Ernest Alfred)
Date:
1903
Catalogue details

Licence: In copyright

Credit: A manual on dental metallurgy / by Ernest A. Smith. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

    277/334 (page 257)
    , GOLD. Material Required.—About 5 grams, (or 75 grains) of 22-carat or other carat gold. Experiment i.—Dissolve the gold alloy in aqua regia ; evaporate nearly to dryness to expel excess of acid; dilute with about a pint of water; add a solution of iron sulphate and gently heat, when the gold will be precipitated as a fine brown powder.* Filter through a filter paper, wash the precipitated gold repeatedly witli water, and warm till perfectly dry. Carefully rub a little of the brown powder with some hard smooth surface, such as a steel or agate burnisher, and note that the characteristic yellow colour and metallic lustre of gold appear. Reserve about .5 gram, (or 5 grains) of the powder for Experiment 14. Transfer the re- mainder to a suitable support and melt into a globule by means of the blowpipe, heating gently at first to avoid loss. Note that it requires a bright red heat to fuse it. E.C2)erimcnt 2.—Determine the density of the gold by suspending it from the arm of a balance by means of fine silk, and accurately weighing it in air. Then place a small vessel of water in such a ]30sition that the gold is completely immersed while still suspended, carefully remove air bubbles by means of a camel's-hair brush, and then note the weight in water. The gold will appear lighter than before, the loss in weight being exactly equal to the weight of an equal volume of the water. Calculate the specific gravity of the gold as follows:— * \\\y of till) n;iif;oiits muiilioiiud uii luigu 96 iiiiiy bo used fur procipitiiting tho gold.