520 M. Carlet on the Formation ofRacemic Acid. 



found cemented in a magnificent manner to a depth of -fo inch. 

 Soda, baryta, and strontia act in the same manner, but this is 

 not the case with lime. This doubtless arises from the fact 

 (which was proved by experiment) that it does not form cyanide 

 of calcium when heated to rednes3 in a current of cyanide of 

 ammonium. 



The action of the various receipts for cementation may be ex- 

 plained by the formation of cyanides. It will be found that in 

 all cases they contain the elements of the formation of alkaline 

 cyanides. 



The production of tartaric acid by the oxidation of milk-sugar, 

 which Liebig discovered, has been already noticed in this Journal*. 

 Carlet f has investigated the action of nitric acid on dulcine, a 

 saccharine substance resembling mannite, which is obtained from 

 Madagascar. He employed, with some modifications, Liebig's 

 process. The oxidation of dulcine had been previously studied 

 by Laurent and Jacquelain, who obtained mucic and oxalic acids. 

 Besides these, Carlet found about 1^ to 2 per cent, tartaric acid, 

 and a saccharine substance which appears to have the formula 

 C 12 H 12 O 12 ; it differs from dulcine in not being coloured yellow 

 by potash, and in reducing oxide of bismuth, which dulcine does 

 not do. 



In addition to these, Carlet ascertained the existence oiracemic 

 acid in quantities of about 1^ per cent, of the dulcine taken. 

 The crystals of this acid were found to be identical with those 

 prepared in other ways, both in form and in chemical properties. 

 A more striking proof was, that it was optically inactive, but 

 could be transformed into dextro-tartaric acid and lsevo-tar- 

 taric acid. This was effected under Pasteur's cooperation by 

 preparing racemate of cinchonidine and exposing it to crystalli- 

 zation. After some days laevo-tartrate crystallized out, and after- 

 wards dextro-tartrate, from which the respective acids were ob- 

 tained. The great interest of this lies in the fact that dulcine, 

 an optically inactive substance, gives rise to a substance which, 

 though also inactive, can be decomposed into two bodies which 

 are capable of deviating the plane of polarization in opposite 

 directions to an equal extent. In the case of Liebig' s experi- 

 ment, tartaric acid, which is a right-polarizing substance, is ob- 

 tained from milk-sugar, which is also right-polarizing. With 

 reference to dulcine, two hypotheses may be made — either that 

 an optically active substance can be obtained from an optically 

 inactive substance, or, which is more probable, that dulcine is 

 only apparently inactive, and is really composed of two substances, 

 one right-polarizing and the other left-polarizing, which just 



* Phil. Mag. vol. xviii. p. 483. t Comptes Rendus, vol. li. p. 37. 



