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

  • Behrens, Heinrich (Theodor Heinrich), 1842-1905.
Date:
1894
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Licence: Public Domain Mark

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

    19/284 (page xiii)
    INTRODUCTION MODERN methods of petrographical research—especially those carried out by the aid of the microscope upon thin sections and crushed fragments—have rendered compara- tively easy the task of discriminating the mineral con- stituents of rocks, by the study of their several physical properties, and especially of their optical characters.1 But in spite of the certainty of the results that can in most instances be obtained by these methods, there constantly arise cases in which it is desirable to confirm or supple- ment the conclusions, thus arrived at, by chemical tests applied to the crystals or fragments of minerals of which rocks are built up. There are two different methods by which the chemical examination of the constituents of rocks may be accom- plished :— I. By employing one or more of the various methods of isolation (which have been brought to a great degree of perfection in recent years) we may separate from the powdered rock a sufficient quantity of each of the indi- vidual minerals composing it, to furnish the materials for 1 A full description of these methods will be found in Rosenbusch's Microscopical Physiography of the Rock-making Minerals, translated by Professor J. P. Iddings. (Macmillan and Co., 1888.)