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.

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    are heated with 5 cubic centimetres of concentrated hydrochloric acid for ten minutes, on a water-bath at a temperature of about 68° Cent. (154° Fahr.), whereby the whole of the cane-sugar is trans- formed into invert-sugar. After cooling, the rotation (in this case left-handed) is observed in a 220 millimetre tube, the temperature of the solution being also noted by introducing a thermometer. The calculation of the percentage of cane-sugar from the above two observations is performed in the following manner:— According to Clerget’s experiments, a solution containing 16‘35 grammes of pure sugar in 100 cubic centimetres—which indicates a rotation of + 100° with a Soleil saccharimeter—will, after inversion, and observed at a temperature of 0° Cent., indicate a rotation of — 44° on the scale, the total change of rotation indicated being 144°. Moreover, it is found that the amount of lsevo-rotation of a solution of invert-sugar varies very markedly with the temperature of obser- vation. The above solution, for instance, would undergo, for every rise of 1° Cent., a reduction of 0'5 division on the Soleil scale, so that at a temperature t°, its amount would be 144 — J t. Putting 8 for the sum of the opposite saccharimetric readings (the readings before and after inversion), that is, for the total decrease of rotation, and t for the temperature at which the inverted solution is observed, the required percentage of cane-sugar R may be found from the proportion whence:— (144 — i *) : 100 = S: R, 100 8 R ~ 144— 4 t ' If, for example, the amounts of rotation were :— By direct observation 94T° right After inversion at temperature 20° Cent. 37*2° left then 8 = 131*3° which gives R = 100 x 131-3 144 - 10 = 98*0 per cent, cane-sugar, instead of the incorrect value, 94-1 per cent., directly obtained from the original solution. Tuehschmid1 has studied minutely the change of rotation pro- duced by the inversion of sugar-solutions, as well as the influence of 1 Tuclischmid: Journ. fur prakt. Cheat. [2], 2, 235.