The use of the blowpipe, in the qualitative and quantitative examination of minerals, ores, furnace products and other metallic combinations / Edited, with emendations, by Dr. Sheridan Muspratt. With a preface by Baron Liebig.

  • Plattner, Carl Friedrich, 1800-1858.
Date:
1850
Catalogue details

Licence: Public Domain Mark

Credit: The use of the blowpipe, in the qualitative and quantitative examination of minerals, ores, furnace products and other metallic combinations / Edited, with emendations, by Dr. Sheridan Muspratt. With a preface by Baron Liebig. Source: Wellcome Collection.

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    by heating the bead strongly, and then quickly removing it from the flame, placing it over a porcelain basin, and striking the wire against the rim; it immediately falls into the basin and solidifies. The quicker this operation is performed, and the firmer the wire is held, the more perfectly is the separa¬ tion of the bead effected. The borax bead melted on the platinum loop, must, when cold, be moistened on one side with the tongue, which side should then be brought in contact with the substance to be tested, in the state of fine grains, or of very fine powder, and the adhering particles melted, together with the borax, in the oxidating flame. In general, earthy substances are better examined when a single particle is at first dissolved, because when the substance is employed in the state of powder, the undecomposed part cannot be well distinguished from the sepa¬ rated and insoluble portions which it may contain. With borax this is not so often the case as with microcosmic salt, as with the latter silicic acid is separated. When the oxidating flame is playing upon the assay, the operator must observe if it dissolve quickly or slowly; whether any gas is generated; if, when entirely dissolved, the glass when held between the eye and the light is colored; and whether the color changes or remains the same on cooling. There are some bodies which, with borax in certain pro¬ portions, give a clear glass when hot or cold, but in the reduc¬ tion, or more particularly in a quick intermittent flame, become opaque, milk-white, or opalescent, and, in some cases, even colored. This reaction is generally observed in such bodies as form clear glasses while melting, but are enamelled on cooling. Such is the case with the alkaline earths, with yttria, glucina, zirconia, oxide of cerium, tantalic and titanic acids, and with some others, as silica, alumina, sesquioxide of iron, oxide of manganese, &c. The presence of silica hinders the phenomenon of the glass becoming enamelled on cooling. The same occurs with those silicates which give a transparent glass only when the assay is perfectly saturated, — oversatu¬ rated, the mass is, on cooling, opaque. When a bead of borax,