Manual of qualitative analysis / by Robert Galloway.

  • Galloway, Robert.
Date:
1861
Catalogue details

Licence: Public Domain Mark

Credit: Manual of qualitative analysis / by Robert Galloway. Source: Wellcome Collection.

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    I. Readily fusible to a bead. II. With difficulty fusible to a bead. III. Readily fusible on the edges. IV. With difficulty fusible on the edges. V. Infusible. 574. “In testing the fusibility of a mineral substance, it should be noticed whether, if fusible, a clear or opaque bead ig obtained; also, whether the substance changes colour, becomes magnetic, or exhibits any phenomena of intumes- cence, ebullition, &¢., all of which are useful characters in indicating the nature of the mineral” (see Appendix D). 575. “Of the metallic oxides, the following only are fusible in the oxidizing flame, viz., the oxides of copper, lead, antimony, and bismuth. Metallic sulphides are, with few exceptions, readily fusible under the blowpipe flame: these exceptions are sulphide of zinc and sulphide of man- ganese.” 576. TREATMENT witH Borax.—To obtain a bead of borax, one end of the platinum wire is bent into a small hook. This is heated in the blowpipe flame, and then dipped into the borax: a small portion of the borax will adhere to it; and this being fused in the flame, and, while hot, dipped again into the powdered borax, a fresh quantity will adhere, which is fused as before ; and this is continued until a bead of the requisite size is obtained. A great many me- tallic oxides dissolve in borax, forming coloured glasses. If any metallic arsenides or sulphides are present, it is neces- sary to roast the substance in the way previously described (556), before making the examination with borax ; and it is frequently advantageous, before roasting the powdered sub- stance, to mix it with a little powdered charcoal, so as to prevent the formation of sulphates and arseniates.