Notices of the proceedings at the meetings of the members of the Royal Institution of Great Britain with abstracts of the discourses . se in a mirror, A is seen reflected as right-handed print, whilst B becomes left-handed print, identical withthe original A. Just the same enantiomorphous relationship as that existingbetween the right and the left hand exists between the molecularpictures of the two lactic acids discovered by Wislicenus and shownin Figs. 3 and 4. Eeference may now be made to the existence of other differencesof an enantiomorphous character between substances which possessenant
Notices of the proceedings at the meetings of the members of the Royal Institution of Great Britain with abstracts of the discourses . se in a mirror, A is seen reflected as right-handed print, whilst B becomes left-handed print, identical withthe original A. Just the same enantiomorphous relationship as that existingbetween the right and the left hand exists between the molecularpictures of the two lactic acids discovered by Wislicenus and shownin Figs. 3 and 4. Eeference may now be made to the existence of other differencesof an enantiomorphous character between substances which possessenantiomorphously related structures. Early in the last century theFrench physicists Arago and Biot showed that a number of substanceshave the power of deflecting the plane of polarisation of a planepolarised light beam thrown through their solutions. Such sub-stances are said to be optically active, and, since the deflection of theplane of polarisation may be either towards the right or towards theleft, the exhibition of optical activity constitutes an enantiomorphousproperty ; optically active substances are conveniently classified. jt 1 ! i 1903.] on Recent Advances in Stereochemistry. 307 as dextro- and laevo-rotatory. Vant Hoff and Le Bel declared thatthe molecules of all naturally occurring substances which exhibitoptical activity when in the fluid state contain asymmetric carbonatoms. All substances, the molecules of which contain an asym-metric carbon atom must possess enantiomorphous molecular con-figurations—similar to those assigned to the two lactic acids—because they exhibit properties of an enantiomorphous character. A very beautiful experiment which the late Sir G. Gabriel Stokesdevised and doubtless exhibited in this room may be so modified asto serve for the demonstration of optical activity. Stokes experi-ment consists in passing a plane polarised beam of light through atall cylinder containing water which has been rendered very slightlyturbid by the addition o
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