Practical microscopy / by George E. Davis.

  • Davis, George E. (George Edward), -1907.
Date:
1889
Catalogue details

Licence: Public Domain Mark

Credit: Practical microscopy / by George E. Davis. Source: Wellcome Collection.

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    The first two are principally used for bleaching vegetable sections, and the strength of the solution may be found in the next chapter. It is most important, when using these reagents, to eliminate every trace of them after the operation is finished, and this may be done by soaking in a bath of neutral sulphite of soda, 15 grains to the ounce of water; a solution of one part of strong liquid ammonia to twenty parts of water will also effect this. Chlorate of potash is generally used for cleaning diatoms, in connection with some strong acid, such as sulphuric, nitric, or hydrochloric. Great care should be used in making these mixtures, as it is easy with them to produce explosions, and their use should (in connection with chlorate of potash) be avoided as much as possible. Nitric acid by itself is a powerful bleacher and oxidiser, but has the disadvantage of emitting powerfully noxious and acid fumes; when slightly diluted to prevent this, its oxidising powers can be increased by the addition of chromic acid or bichromate of potash. This admixture is not in the least likely to explode. Another extremely powerful oxidiser is a mixture of strong sulphuric acid and chromic acid in crystals; it is especially useful in cleansing diatoms, and must be heated carefully over the spirit-lamp to obtain its maximum effect. Peroxide of hydrogen is an extremely valuable bleaching agent and oxidiser, and likely to come into general use when its properties are better known to microscopists ; it is neither acid nor alkaline, and does not give off any objec- tionable odour. Another bleaching agent is turpentine, almost exclusively used to reduce the intensity of colour in the chitinous skeletons of insects. After having been treated with potash or soda solution, and the abdominal contents expressed, the insect is washed with water, dried in alcohol, and allowed to soak in turpentine until the colour of the ctiitin is sufficiently reduced in intensity. Turpentine has