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

  • Landolt, H. (Hans), 1831-1910.
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.

    227/320 (page 207)
    239*3°) and hence the preparation under examination must have been free from admixture. Three other samples of commercial sulphate of quinine, exa- mined under like conditions, gave the following specific rotations respectively:— - 236-6°, - 235-5°, + 109-5°. Of these the two first agree so nearly with the normal value that no admixture of foreign substance, at least in any appreciable quantity, could have been present; the third, on the contrary, shows such a marked rotation to the right, that it must contain a notable amount of quinidine and cinchonine. In this way Hesse showed that a so-called quinidine disulphate of English houses is an essentially different product from pure quinidine (conchinine) sulphate as prepared by the firm of F. Jobst, of Stuttgart. These preparations exhibited the following differences : — Quinidine (conchinine) sulphate, with 4 mols. H Cl c = 2 1 (anhydrous salt) ’ English quinidine sulphate, with 4 mols. H Cl, c = 2 (anhy- 1 drous salt) ) Quinidine (conchinine) sulphate, with 4 mols. H2 S04, c — 2 1 (anhydrous salt) . . . . . . . . ) English quinidine sulphate, with 4 mols. H2 S04, c — 2 } (anhydrous salt) . . . • . . . . J [«]d — + 286°. [«]»= + 264°. [«]D = + 280° to 282°. [«]D = + 247-5°. The direct optical analysis of alkaloids in cinchona-bark extracts is, as Hesse remarks, beset with difficulty from the solutions contain- ing a yellow colouring matter, which cannot be removed alone, and which impedes accurate observation of rotation. Hence the polar- iscope cannot serve for the direct valuation of cinchona-barks, although it provides a useful check on the results obtained by other modes of analysis. § 106. Optical Analysis of Mixtures of Cinchona Alkaloids.—The quantitative composition of a mixture of two alkaloids may be deduced from its specific rotation with the aid of the values given in § 103. To test this method Hesse1 determined the specific rotations of a number of mixtures of known composition, to ascertain whether the former could be deduced from the rotatory powers of the constituents. This was found to be sufficiently exact, and there- 1 Hesse: Liebig's Ann. 182, 146.