to 3·88. [a];= +211°. Starch solution heated with dilute sulphuric acid at 100°, gives first [a]; = 216, but the rotatory power quickly decreases with the formation of dextrin and dextrose. Béchamp (A. C. P. [3] 48, 458). Glycogen. Dextro-rotatory. Various modifications. [a];= +140 to 211. Tichanowitsch. Stscherbakoff (J. B. 1870, 848). = Inulin. Lævo-rotatory. The data for dahlia- and elecampaneinulin, range from [a]; 26 to 72. The inuloid of Popp (L. A. 156, 190), C H10 05 + H2O, with c = 2, gives [a]; = — 30·5. The rotatory powers of the acetic ethers of cellulose, starch glycogen, and inulin have been determined by Schützenberger (L. A. 160, 74). Dextrin. Dextro-rotatory. The data range from [a];= 139 to 213. Gum Arabic Acid. The varieties of gum arabic met with in commerce, are partly dextro-rotatory, and partly lavo-rotatory. Scheibler (D. C. G. 1873, 618) found, on examination of five samples in aqueous solution with c = 5, the specific rotations for [a] = +373 +46·1; 28.8; 29-2; -300 respectively. On heating with dilute sulphuric acid, all these solutions become dextro-rotatory by the formation of gum-sugar (arabinose), C, H12.06. The gum of beet-root is, in general, dextro-rotatory, but at certain seasons and in individual plants it is found to be lævorotatory. Scheibler, loc. cit. Dextro-rotatory gum is further found in the stag-truffel, and lævo-rotatory gum in couch-grass. Ludwig (J. B. 1869, 791; 1872, 803). Water. p = 2.78. [a]; = (65.17 0.63 c). Hesse (L. A. 176, 116). 73.4. Biot and Pasteur (C. R. 34, 607). Populin, C20 H22 Og. Lævo-rotatory. = Water. p 1. [a]; = 53. Biot and Pasteur, loc. cit. Phlorhizin, C2H30 011 + 2 H2O. Lævo-rotatory. Alcohol of 97 per cent. (by vol.) Alcohol. c = 1 to 5. t = 22.5. [a]D = (49.40+ 2.41 c). Hesse (L. A. 176, 117). Wood Spirit. p = 3.9. [a]D [a]D p = 4.6. = = § 114. Derivatives of the Sugars. Besides the previously-mentioned nitric and acetic ethers, active amyl-alcohol and active lactic acid belong to this group. Active amyl-alcohol. Lævo-rotatory. Commercial fermentation. Amyl-alcohol gave, in a layer 1 decimetre deep, an angle of rotation [a]D - 1.97 (Le Bel); [a]D= =276 ( 40 of Ventzke's scale for a length of 5 decimetres. (Ley.) = For the active amyl-alcohol obtained from the commercial product by separation as completely as possible from admixture with the inactive alcohol by Pasteur's or Le Bel's method, we have the following data: (a) Specimens obtained by Pasteur's method of fractional crystallization of amyl-sulphate of barium. (b) Amyl-alcohol, purified by Le Bel's method, by repeated treatment with hydrochloric acid gas, whereby the inactive portion is first converted into amyl-chloride and can then be removed by distillation. Boiling-point, 127°. 1 1° Ventzke [ray j] = 0·3457 angular degrees for ray D. ap 453 to 463 for 1 decimetre. given; but taking it as = 0.81, we get [a]D (Bull. soc. chim. [2] 21, 542). = By repeated distillation with caustic potash, and still more quickly with metallic sodium, active amyl-alcohol is rendered inactive. Le Bel (Bull. soc. chim. [2] 25, 545). Lævo-amyl-alcohol by repeated distillation with caustic soda becomes dextro-rotatory. að = + 2° for 1 decimetre according to Beignes Bakhoven (Pogg. Supp. Bd. 6, 329); but this is denied by Le Bel (Bull. soc. chim. [2] 25, 199) and Balbiano (D. C. G. 1876, 1692). According to Pierre and Puchot aqueous amyl-alcohol gives a stronger rotation than the anhydrous alcohol. Ley (D. C. G. 1873, 1370) is, however, unable to confirm this. (b) From Leucin. ap 1·18 for 1 decim. (17 divs. Ventzke for 5 decims.) Erlenmeyer and Hell UD = 4.3 for 1 decim. (40 divs. Soleil for 2 decims.) d 0.874 at 0°. [α]D = 0.869 at 15°. [a]D = Boiling-point 186°. Ley (D. C. G. 1873, 1369). = 8.7. = 4.9. a = 2.3 for 1 decim. (33 to 34 divs. Ventzke for 5 decims.) Erlenmeyer and Hell. (L. A. 160, 289). = The following derivatives from lævo-amyl-alcohol, giving an angle of rotation ap 4.63 for a length of 1 decimetre, have been prepared and examined by Le Bel (Bull. soc. chim. [2] 21, 542) :— Amyl-chloride (boiling-point 97° to 99°). Dextro-rotatory. a = 1.10 for 1 decim. d = 0·886 at 15°. [a]d = 1.24. Amyl-bromide (boiling-point 117° to 120°). Dextro-rotatory. [a] = 3·75. Dextro-rotatory. [a]D = 5.34 to 5:41. 8.22 to 8.33 for 1 decim. d = 1.54 at 15°. Methyl-amyl and amylene from active amyl-alcohol are inactive. (Le Bel.) The following other derivatives of amyl-alcohol and valerianic acid have been examined by Pierre and Puchot (C. R. 76, 1332) :— The stability of the active amylic grouping is shown by the researches of Wurtz (L. A. 105, 295), in which amyl-iodide was converted into the cyanide (ared = 1·59° for a length of 1 decimetre), this into capronic acid (ared = 1·22°), and this, again, by electrolysis, into di-amyl (ared = 3.20°). Para-lactic acid, Active sarco-lactic acid. Dextro-rotatory. The investigations of Wislicenus (L. A. 167, 302) have shown that an exact determination of the specific rotation of para-lactic acid is impossible as this substance, even at ordinary temperatures, passes gradually into the ether-anhydride, Ce H10 Og, and into lactide, CH, O2, both of which are strongly lævo-rotatory. Freshly prepared, it shows in aqueous solutions, in which the degrees of concentration were determined by titration (reckoned as C, H, Og), the following specific rotation : By standing, the rotation of the solutions gradually increases. If they be then diluted with water a sudden decrease of rotation takes place, which, however, gradually increases again, but without returning to its original amount. For example, two, specimens of equal concentration gave the following results: : c = 21.24. 6 The gradual increase here observed is due to the gradual conversion of the lævo-rotatory molecules of the anhydride, C H10 05, originally present in the solution, into the dextro-rotatory molecules of the acid C, H, O3, which, moreover, is proved by the fact that, if we neutralize the liquid with alkali, it gradually recovers its acidity. The decrease of rotatory power on the adition of water, is explained by Wislicenus to be caused by the formation of the hydrate, C, H, O3 + H2O, to which he assigns a rotatory power inferior to that of the acid itself. 2 It requires but 2 or 3 per cent. of the anhydride to be present to give the solution of lactic acid distinct lævo-rotation. But in preparations that have been long kept the amount of rotation becomes considerable. Thus, a solution which had been kept in vacuo over sulphuric acid for a year and nine months, and whose composition approximated very closely to 84 per cent. Cg H10 О5 + 16 per cent. C, H, O, gave in alcoholic solution with c = 1954, the specific rotation [a] = -85.9°. 3 4 Zinc para-lactate, Zn (Cg H. O3)2 + 2 H2O. 10 Lævo-rotatory, The specific rotation in aqueous solution appears to increase with decrease of concentration. |