MM. Schmidt and Dessaignes on Tartaric Acid. 49 



that acid. Kolbe considers that they bear to succinic acid a 

 relation analogous to that which he considers lactic and glyceric 

 acids to bear to propionic acid. That is, malic acid is oxysuc- 

 cinic acid, and tartaric acid is dioxysuccinic acid, as is seen from 

 the formulae — 



HO, C 4 H 5 (C 2 O 2 ) 2HO, C 4 ^*(% ™W. 



Propionic acid. . . \ . , / 



Succinic acid. 



HO, C*|^ (©■ 0*) 2HO, C< H^J (g 0^ Q2 



Oxypropionic acid Oxysuccinic acid 



(lactic acid). (malic acid). 



C 4 H 3 "1 H 2 "1 



HO, HO 2 I (C 2 O 2 ) 2 HO, C 4 HO 2 I ( £ 2 £ \ O 2 . 

 H0 2 J HO 2 J V L u / 



Dioxypropionic acid Dioxysuccinic acid 



(glyceric acid). (tartaric acid). 



Schmidt has, from this point of view, made a series of experi- 

 ments* on the action of reducing agents on malic and tartaric 

 acids ; and he has found that they may be converted into suc- 

 cinic acid by the use of the reducing agent, hydriodic acid, by 

 which Lautemannf effected the transformation of lactic acid into 

 propionic acid. The change was found especially easy with 

 malic acid. When a concentrated aqueous solution of hydriodic 

 acid was saturated with malic acid, and the mixture heated in a 

 sealed tube for some hours to a temperature of 130°, a large 

 quantity of iodine along with some brown crystals separated. 

 The latter were succinic acid coloured with iodine. They were 

 readily purified, and gave correct numbers on analysis. The 

 change is thus expressed : — 



C 8 H 6 io + 2HI = C 8 H 6 8 + 2HO + 2I. 



Malic acid. Hydriodic Succinic 

 acid. acid. 



The transformation of tartaric into succinic acid took place 

 with greater difficulty. It also was effected by saturating a con- 

 centrated aqueous solution of tartaric acid with hydriodic acid 

 gas, and heating the mixture in a sealed tube to a temperature 

 of 120°. The contents of the tube were then boiled in a retort, 

 with frequent additions of water, until the iodine and hydriodic 

 acid were removed, then evaporated to dryness, and treated with 

 ether to remove the last traces of iodine, and finally, the succinic 

 acid repeatedly crystallized from ether to free it from an admix- 



* Liebig's Annolm, April 1860. 

 f Phil. Mag. vol. xix. p. 384. 

 Phil Mag. S. 4. Vol. 20. No. 130. July 1860. E 



