A manual of microchemical analysis / by H. Behrens ; with an introductory chapter by John W. Judd.

Date:
1894
Catalogue details

Licence: Public Domain Mark

Credit: A manual of microchemical analysis / by H. Behrens ; with an introductory chapter by John W. Judd. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    will answer. After rinsing and drying the specimen is examined under a low power, first lying flat on the stage, afterwards conveniently inclined. § 91. Testing for Carbonates Carbonates diffused through a rock are detected by putting a drop of water on the specimen, covering it and adding a drop of acid in contact with the cover glass, and a narrow strip of filtering-paper on its opposite side. As the water is sucked up, the acid will creep in between the cover glass and the slice of rock, evolving bubbles of carbonic acid, which are speedily arrested by the cover glass. A more elaborate method is described in Part I., § 40, b. % 92. Staining of Etched Specimens The silica of minerals decomposed by acids may be stained with coal-tar dyes. Fuchsine, pointed out by the author in 1871, and once more recommended by him in 1882, and by Haushofer in 1885, has come into general use. Its staining power is very great, and the bluish-red stain comes out with a strong contrast against the surrounding minerals. It must, however, be abandoned, because it is not fast in the presence of light or Canada balsam, and is apt to give accidental films wherever the surface of the specimens is not quite smooth. Malachite green is free from these defects, while it surpasses fuchsine in staining power. It is freely soluble even in cold water. Methylene blue. comes very near it in staining power and solubility, but it is not quite free from the defect of forming accidental films. Saffranine of commerce (tolusaffranine) is less soluble than the former. It requires hot water and does not give