grammes c of active substance per 100 cubic centimetres of solution may be found from the equation Similarly, the proportion of an active solid substance in admixture with inactive substance can be found by dissolving a known weight, p, to a given volume, v cubic centimetres; then the percentage of solid substance present is represented by: Of course, it is here assumed that the inactive ingredients present in solution exert no influence on the specific rotation of the active substance. (b) In certain cases also, for the quantitative analysis of mixtures of two active substances, as in the case of the cinchona alkaloids, §§ 106, 107. The values cannot, however, be applied in any way for comparison of the rotatory powers of different active substances with each other, as they refer only to solutions of a given composition, and do not represent the actual specific rotation of the pure substance itself. All the specific rotations hereafter given, refer to the compounds of the exact composition denoted by the chemical formulæ annexed; so that, where the substance contains water of crystallization, the values refer to the hydrated substance. If the specific rotation of the anhydrous substance is required, it can be calculated from the formula in which M represents the molecular weight of the hydrated substance, and m that of the anhydrous substance. As before: [a], [a]; denote respectively the specific rotation for ray D and for the transition tint j. a denotes angle of rotation for a layer 1 decimetre thick. (concentration) the number of grammes of active substance in 100 cubic centimetres of solution. (percentage composition) the number of grammes of active substance in 100 grammes of solution. specific gravity of the solution. temperature (Cent.) at which the rotation has been observed. In referring to memoirs the following abbreviations have been adopted :— stands for Liebig's Annalen der Chemie u. Pharmacie. Journal für praktische Chemie. Berichte der deutschen chemischen Gesellschaft. Zeitschrift des Vereins für Rübenzuckerindustrie des deutschen Reichs. L. A. D. C. G. K. Z. J. Cane-Sugar, C12 H22 011. Dextro-rotatory. Aqueous solu tions. Tollens (D. C. G. 1877, 1403) gives the annexed formulæ : 1. Specific gravity of solutions at 17.5° Cent. referred to that of water of 4° Cent. Rotation observed at 20° Cent. 2. Specific gravity of solutions at 17.5° Cent. referred to that of water at 17.5° Cent. Rotation at 20° Cent. experiments referred to in § 37 gives the formulæ : 1. Specific gravity of solutions at 20° Cent. referred to that of water at 4° Cent. Rotation observed at 20° Cent. = 35 to 98. [a]D = 64 156 C051596 q - 0.00028052 q2. 2. Specific gravity of solutions at 20° Cent. referred to that of water at 17.5° Cent. Rotation at 20° Cent. c = 0 to 10. [a], = 68.65 0.828 +0·115415 c2 0.0054167 c3. Previously, the following values of [a] had been given, without taking into account the alterability of the rotation1 :— The specific rotation for different rays has been determined, according to Broch's method, by Arndtsen (A. C. P. (3) 54, 403) and by Stefan (Sitz.-Ber. d. Wiener Akad. 52, II. 486). Arndtsen, employing solutions with 30 to 60 per cent. of sugar, obtained the following mean values: Stefan, with solutions wherein p = 10 to 30 per cent., obtained [a] [a] 84.56 87.88 The latter values can be derived from the = 2538 12 - 5.58, taking the wave-length λ in ten-thousandths of a millimetre. = 1 As the specific rotation observed by Girard and Luynes, and also by Calderon with sugar solutions, in which c = 10 to 20, viz., ([a]n 67.1 to 67.3) differs considerably from 66.5, the result obtained by Tollens and Schmitz, Tollens crystallized afresh some pure sugar, and examined the rotation in several crops (D. C. G., 1878, 1800). He obtained with c = 10 the value [a]D 66.48. (Specific gravity of the solutions at 17.5° Cent. with reference to that of water at 4° Cent.) The value 67 is certainly too high. Adopting Montgolfier's ratio, ap: a; 1: 1129, in the case of sugar (§ 18, p. 43) we get, if [a]D=66·5, [a];=75·08. With Weiss' co-efficient 1·034 (§ 18), [a]; = 68-76. = 5.5, [a], 78.32. Stefan's dispersion-formula gives for λ; = In alcoholic solutions, cane-sugar exhibits higher rotatory power than in aqueous solutions (R. Z. J. 1877, 803).. Hesse (L. A. 176, 97) found that in solutions containing 50 per cent. of alcohol, with c = 5, and t = 15°, [a]D = 66.70. No further estimations were made. Sulphuric acid appears to increase the rotation. Hesse (L. A. 176, 97) employing the proportion: 1 mol. sugar (c = 6) to 1 mol. H, SO+water to 100 cubic centimetres with t = 15°, obtained [a]D = 66:67. Alkalies diminish the specific rotation of cane-sugar. 1 mol. sugar + 1 mol. Na, 0.c = 5. t = 15°. [a]D 66.00. Hesse (L. A. 176, 97). = According to Sostmann (R. Z. J. 1866, 272) the saccharimetric estimations of sugar in presence of alkalies, come out too low by the following amounts :— Pellet (R. Z. J. 1877, 1036) gives the following values :— Lime causes a remarkable reduction of rotatory power. (R. Z. J. 1876, 737) records the following observations : Müntz Saccharimetric observations by the following observers have shown that the addition of 1 part of lime destroys the rotatory power of: 0.64 part sugar according to Jodin (C. R. 58, 613). The action of the lime is removed by neutralization with acetic acid. 1 part baryta destroys the rotation of 0.426 parts sugar, according to Bodenbender. when c = 5.4 when c = 17.3 Pellet. Salts of the alkalies exert a similar action. Müntz (R. Z. J. 1876, 735) investigated the effects of the following salts on the specific rotation, which was taken for the pure sugar as [a] = 67·0, and obtained the results subjoined: : |