o8i 



Artici^e XXIX. 



On the Application of Circular Polarization to Organic 

 Chtmistry ; hy M. M. Biot and Chevreul. 



On the Application of Circular Polarization to the Aiialyais 

 of the Vegetation of the Graminece; by M. BroT. 



(Read before the Royal Academy of Sciences of Paris, July 1st, 1833.) 

 From the Notcvelles Annates du Museum d'Histoire Nafurelle, vol. iii.,p. 47, ij. 



J.T being my intention to show by experiment in what nicinner indica- 

 tions derived from circular polarization may be usefully employed in 

 chemical researches, principally in those of organic chemistry, the 

 innumerable transformations effected in carbonated products by vege- 

 table life appeared to me to be one of the objects of study best adapted 

 for the attainment of this end. For these products, so various in their 

 appearances and physical properties, being, under an infinity of circum- 

 stances, composed solely of carbon and water united in different pro- 

 portions, their mixtures, combinations, and transmutations, offer ex- 

 cellent tests of a method which distinguishes them individually by 

 inspection alone, and thus ascertains their presence without altering 

 them. Now organic chemistry was deficient in precisely these cha- 

 racters recognisable by inspection, the consequence of which was its 

 difficult, I may even say its often uncertain progress; because, being 

 unable to recognise bodies otherwise than by isolating them, and this 

 isolation being effected only by the intervention of special agents 

 applied to the combinations or mixtures of which they form a part, the 

 choice and appropriation of the tests to be employed for each case 

 could only be determined by the conjecture, more or less probable, of 

 their presence ; and there is often danger of modifying these products 

 by thus acting upon them, or even of creating new ones by uniting the 

 principles of which they are formed ; so mobile are the combinations 

 upon which they depend, and with such facility do they become con- 

 verted into each other. 



The indications (caracteres indicatifs) furnished by circular polari- 

 zation certainly will not remove these last-mentioned difficulties, which 

 are inherent in the subject ; but in very many cases they will abridge 

 and reduce them to those which are inevitable, by in the first instance 

 furnishing the chemist with the properties capable of being immediately 

 observed, predicable of the molecular condition of the combinations on 

 which he has to treat; then by rendering equally visible and observable 

 all the changes by which that primitive state mav be altered, so that 



