8 



Mr. J. E. Marsh. Researches on the [Dec. 5 r 



apposite isomers, in the sense namely in which dextro- and lsevo- 

 tartaric acids are regarded as optically opposite. 



In its ordinary properties the lsevo-acid differs markedly from the 

 dextro-isomer. It has a lower melting point, namely, 170° C, as 

 compared with 185 0°. Again it yields a very soluble amorphous 

 barium salt, the corresponding salt of the dextro-acid being also 

 indeed very soluble but crystalline. A more remarkable distinction, 

 however, is that the lsevo-acid appears to have no corresponding 

 anhydride. When subjected to the action of acetyl chloride, an 

 important reagent employed by Anschiitz for obtaining the anhy- 

 drides of dibasic acids, the dextro-acid readily and practically quanti- 

 tatively yields its anhydride, which is insoluble in carbonate of soda. 

 The lsevo-acid, on the other hand, when treated in the same manner, 

 yields a product almost completely soluble in carbonate of soda, from 

 which the original acid of melting point 170° is recovered apparently 

 unaltered. 



Conversion of the Lcevo- into the Dextro- Acid. 



If, however, the la3vo-acid be distilled, it boils about 294° C.^ 

 yielding the anhydride of the ordinary dextro-camphoric acid, from 

 which anhydride this acid may be obtained in the ordinary way. 



Thus it appears possible to convert any quantity of the dextro-acid 

 almost entirely into the lasvo- through the intervention of the chloride, 

 and any quantity of the laevo- back again to the dextro- by means of 

 the anhydride. 



Mixture of the two Acids. 



Chautard obtained a laevo- camphoric acid by the oxidation of a 

 lsevo-rotatory camphor. This acid is described as possessing all the 

 properties of ordinary camphoric acid, except that its rotatory power 

 is of opposite sign. Further, when strong alcoholic solutions of the 

 two acids are mixed there is a precipitation of crystals and a rise of 

 temperature in the liquid. 



The lsevo-acid which I have obtained differs from Chautard's in 

 other properties, and also in this, that when mixed with the dextro- 

 acid in equal quantities in strong alcoholic solution there is no 

 crystalline deposit and no rise of temperature. 



On boiling down the alcoholic solution, a syrupy residue is left, 

 which dissolves in hot water more readily apparently than either of 

 its constituents. From the aqueous solution it separates partly as an 

 oil, which after a time solidifies, and partly as crystals. Neither the 

 solidified oil nor the crystals have a definite melting point, but both 

 melt at a lower temperature than either of the component acids. 

 Hence the two acids do not appear to form any definite compound 

 camphoric acid. 



