232 THE PREPARATION OF 



light petroleum ; the relatively large quantity of even care- 

 fully dried solvent thus necessary tends, however, to the 

 introduction of traces of water and consequent formation of 

 more free acid. In absence of water the decomposition of 

 the intermediate compound proceeds very slowly, and it is 

 necessary to assist the decomposition by application of heat. 

 After decomposition is complete a glass is obtained on extrac- 

 tion with benzene and subsequent removal of the solvent, 

 the analytical figures for which agree nearly with those 

 required for a compound [C 6 H 5 .CHOH.CO] 2 O, while the 

 figures obtained on titration point also to this formula. 

 From this substance, which still contained a trace of sulphur, 

 mandelic acid was regenerated by treatment with water or 

 by dissolving in sodium hydroxide solution and acidifying, 

 though a small portion remained undissolved by the solvents. 

 The intermediate compound formed from silver malate is 

 more easily decomposed, and most of the sulphur dioxide can 

 be expelled by passing carbon dioxide through the ethereal 

 solution for a day or two. After distillation of the ether, 

 soft feathery crystals separate from the residual syrup, and 

 these, after washing with ether and recrystallisation, give 

 analytical figures which agree nearly with those required for 



CH(OH)COv 



malic anhydride )>0. The substance is soluble 



CH 2 .CO / 



in water, and malic acid is formed in the aqueous solution 

 on standing. This substance is probably not the same as 

 the porcelain-like anhydride of malic acid obtained by Walden 

 (Ber., 1899, 2706, 2819). It appears to be opticaUy active. 

 A fuller investigation of these interesting compounds must 

 be deferred until they can be prepared more easily and in 

 larger quantity. The experimental difficulties met with in 

 their preparation are at present considerable. 



Attempts to prepare normal anhydrides of the amino- 

 benzoic acids were unsuccessful by both methods. 



