han the true specific rotation of pure oil of turpentine (37·01), differng from the latter in proportion to the diluteness of the solutions mployed in its determination. Thus, with alcohol as the inactive On the other hand, if we adopt the formula [a] = A + B q + C q2, nd compute the values of the constants A, B, and C from the olutions containing the smallest, mean, and largest proportions espectively of the inactive constituent, we get for A a value pproaching very near to that of the specific rotation of pure oil of urpentine. Moreover, the formula agrees sufficiently well with the experimental curve throughout (from q = 10 to 90). The mixtures specified furnished the results shown below: 1. Alcohol (computed from solutions I., III., and V.) [a]D = 36.974 +0.0048164q +0.00013310 q2. 2. Benzene (computed from solutions I., IV., and VII.) [a]D 36.9700-021531g + 0.000066727 q2. 3. Acetic acid (computed from solutions I., IV., and VI.) 36.8940·024553 g + 0·00013689 q. [a]D = If now we seek to determine the specific rotation of pure oil of turpentine from the more dilute solutions only, we get for A in the formula [a] = A + Bq + Cq values showing the following divergences: Hence the divergence from the real value may amount, in some cases, to a whole degree, when the solutions contain more than 50 per cent. of solvent. II. RIGHT-HANDED OIL OF TURPENTINE. § 31. The American oil here employed had a specific gravity of 0.91083. For determining the rotation of the pure oil and its mixtures Wild's and Mitscherlich's instruments were used, but at the time these observations were made the experimental tubes had not been furnished with water-baths. The temperature of the liquid was ascertained at the conclusion of the measurements by a thermometer inserted into the tube. the three points lie almost exactly in a straight line. Introducing mean value of [a] into the formula [a] = A + B q, we obtain1. Calculated from mixtures I. and II. A 14.189 B = + 0011415 The values here obtained for A agree very closely with the directly observed specific rotation of the oil, 14·147°. = Taking the mean of the above values for A and B, respectively, = 14173 +0.11782 q, [a]D which, of course, corresponds closely with the observations. We have A further series of experiments with benzene as solvent led to no result, as the oil of turpentine used in preparing the mixtures was not uniform, from not all having been kept an equal length of time exposed to oxidizing influences. III. NICOTINE (LEVO-ROTATORY). $32. The pure substance here employed was prepared from 400 grammes commercial nicotine (supplied by H. Trommsdorff, of Erfurt). To remove any small impurities of ether, alcohol, and water, the liquid was heated in a retort, whilst a stream of hydrogen passed over it, for eight hours, at a temperature of 150°, which was finally raised to 180° Cent., whereby a total distillate of 15 cubic centimetres, consisting chiefly of alcohol, passed over. The residue was then distilled in a current of hydrogen, in successive portions of 200 grammes, from a small retort heated by a sand-bath. At 225° Cent. the nicotine, at first still retaining some water, began to pass over, but the thermometer immersed in the liquid quickly rose to 244° (corrected, 249° Cent.) when the boiling proper began. Raised into the vapour, the thermometer fell to 241.5° to 242° (corrected, 246.6° to 246·8° Cent.), which temperature remained constant during the rest of the distillation. Height of barometer, 745 millimetres. The hydrogen was admitted in a very slow stream, and no decomposition of the substance resulted. Altogether 350 grammes of pure substance, in the form of a colourless liquid, faintly tinged with yellow, were obtained. It was sealed up in glass tubes. An analysis of this nicotine, the nitrogen being determined in the gaseous form, gave the following numbers: The preparation was submitted to further examination by titration. The nicotine was weighed in thin glass bulbs, which were then broken under water, and, after solution, tincture of litmus added, |