Handbook of the polariscope and its pracitcal applications / adapted from the German editon of H. Landolt, by D.C. Robb and V.H. Veley.

  • Hans Heinrich Landolt
Date:
1882
Catalogue details

Licence: Public Domain Mark

Credit: Handbook of the polariscope and its pracitcal applications / adapted from the German editon of H. Landolt, by D.C. Robb and V.H. Veley. Source: Wellcome Collection.

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    in a retort provided with an upright condenser, and, whilst the retort is kept filled with carbonic acid at the ordinary pressure of the atmosphere, the contents are raised to boiling, whereby a temperature of 160° to 162° Cent, is attained, no change of rotatory power can be detected at the end of sixty hours. But such change occurs when the temperature passes beyond 250° Cent, in a sealed tube. A sample of English right-rotating turpentine-oil, which gave an original deviation of a, = + 18‘6° in a layer of 100 millimetres, showed the following angles of rotation at higher tern- peratures:— After 4 hours at 250° Cent. aj* = + 15 3^ After an additional 4 „ „ 250° to 260° Cent. a,. = + 11'8° 60 „ „ 250° to 260° Cent. Oj. = - 8’6^ 42 „ „ about 300° Cent. aj. = - 5*6° At a certain stage an inactive mixture of right-rotating and left-rotating molecules must therefore have been present (Berthelot1). Polymerization occurs simultaneously with the above changes. This can readily be produced without any change of temperature, by treating with antimony trichloride, whereby, for example, left-rotating terebenthene is converted into right-rotating tetra- terebenthene (Riban2). In certain cases, two isomeric derivatives possessing opposite rotatory powers but of unequal intensity are simultaneously formed from an active substance, the immediate product being therefore also active. By heating mannite to 150° Cent., or treating it with muriatic acid, we obtain a right-rotating mixture, which on evaporation separates out the crystallizable laevo-mannitan, leaving amorphous dextro-mannitan in the mother liquor (Bouchardat ). Again, cane-sugar is transformed by the action of ferments or dilute acids into left-rotating invert-sugar, which can be split into right- rotating glucose (dextrose) and left-rotating glucose (kevulose). On the other hand, cane-sugar exposed with one-twentieth part water, m a sealed tube, for the space of two or three minutes, to a temperature of 160° Cent., gives an inactive glucose, which appears to be in- divisible (Mitscherlich,4 Muntz and Aubin5). 1 Berthelot: Ann. Chim. Phys. [3], 39, 10. 2 Riban: Bull. Soc. Chim. [2], 22, 253. Jahresb. fur Chem. 1874, 451. 3 Bouchardat: Jahresb. fur Chem. 1875, 792. 4 Mitscherlich : Lehrbuch der Chem. 4 Aufl. I, 337. 5 Miintz and Aubin: Ann. Chim. Phys. [5], TO, 564.