Volume 1

Methods of practical hygiene / translated by W. Crookes.

  • Karl Bernhard Lehmann
Date:
1893
Catalogue details

Licence: Public Domain Mark

Credit: Methods of practical hygiene / translated by W. Crookes. Source: Wellcome Collection.

    71/468 page 43
    In many substances [«D] decreases for some time after the preparation of the solution (birotation). Thus, a solution of glucose does not reach its minimum of rotation until thirty hours after the preparation of the solution; it then remains constant. It is assumed, by way of explanation, that the groups of molecules which rotate more strongly are split up the course of this time into molecules which rotate m normally. It follows as a practical rule that all solutions prepared for comparison must be allowed to stand for about thirty hours. Compare Pribram, Berichte der Deutsch. Chem. Gesellschaft, xxi. Table of the value of [«D], at temperatures of 15J to 20 ', for some of the more important substances in dilute solutions up to about 5 per cent:— Cane sugar, CloHo.)011 . . . + 66’5 Milk sugar, C12H02On + H20 . . . + 54+ Maltose, C12H22On + H20 .... +140-8 Fruit sugar (dextrose), C6H1206 . . + 51*8 Fruit sugar (levulose) j at higher temperatures) —100 ^ \ the deflection decreases >- greatly 1 + 139 to 213 Invert simar Dextrine . Serum albumen 56 For more complete tables see Beilage zum Chemiker Kalendar, Berlin, Springer, a new edition yearly. An excellent account of the entire subject, theoretical and practical, is found in Landolt, Das OjUische Dreliungsvermogen, &c., Brunswick, 1879.1 5. Measurement and Calculation. (Supplementary to Chaps. I. to IY.) § 31. In scientific researches all magnitudes are stated according to the metric system, using the following abbre- viations :— Measures of Length.—1 metre (m.) = 10 decimetres (dm.) = 100 centimetres (cm.) = 1000 millimetres Jiimh); 10 metres = 1 dekametre (Dm.); 100 metres = 1 hectometre (Jim.); 1000 metres = 1 kilometre Jem.) ; 10,000 metres = 1 myria- 1 See also Ganot's Physics, translated by E. Atkinson. Eleventh edition. London : Longmans, 1883. — Translator.
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