Oct. 22, 1921 Acids of Pyrus coronaria, Rhus glabra, Etc. 223 



It will be observed that if malic acid had been present in the cold water 

 extract, it would have been discarded with the mother liquor from the 

 first crop of succinic acid crystals, since malic acid is not only very deli- 

 quescent but likewise difficult to crystallize from solutions containing 

 sugars and other impurities. Some malic acid was doubtless lost at 

 this point, but the large yield of succinic acid indicated that it was the 

 chief acid derived from the fruits which had undergone autolysis. 



It was of course a matter of interest to find out whether or not succinic 

 acid was present also in the living fruit. A new supply of crab apples was 

 therefore heated with water in an autoclave at 20 pounds pressure, and 

 the juice, after filtration through cloth, was evaporated to a small volume 

 and treated with several volumes of alcohol, to throw out pectin and 

 other colloids insoluble in alcohol. The alcohol was distilled from the 

 filtrate, which was concentrated, in vacuo, to a sirup. From this sirup it 

 was impossible to obtain even a trace of succinic acid, by either of the 

 methods which had been successfully used with the cold water extracts. 

 It contained, on the other hand, a large quantity of malic acid, identified 

 by the preparation and analysis of its silver salt. The concentrated sirup 

 mentioned above was diluted with water, which brought about a sepa- 

 ration of a small precipitate of red pigment, which was filtered off. When 

 lead acetate was added to the filtrate, the acidity of the solution was so 

 great that the first increment caused no precipitation of lead malate but 

 did throw out a small amount of dark precipitate, which was of course 

 removed. Further addition of lead acetate gave a voluminous precipi- 

 tate of lead malate (A), which was filtered off and washed. A second 

 yield of lead malate (B) was obtained from the solution by the addition 

 of alcohol. The two precipitates were separately decomposed with 

 hydrogen sulphid, neutralized with sodium hydroxid, and silver nitrate 

 solution was cautiously added. The first few drops of the silver nitrate 

 produced a dark precipitate which was removed by filtration. Further 

 addition of silver nitrate caused white silver malate to separate. The 

 precipitates were dried at 105 C. and analyzed as follows (two samples 

 each from A and B) : 



(I) 0-5317 gin- salt from A gave 0.3315 gm. Ag. 



(II) 0.7249 gm. salt from A gave 0.4518 gm. Ag. 



(III) 0.3067 gm. salt from B gave 0.1882 gm. Ag. 



(IV) 0.5374 gm. salt from B gave 0.3303 gm. Ag. 



Foimd: (I) 62.34 per cent; (II) 62.32 per cent; (III) 61.36 per cent; (IV) 61.46 

 per cent. 



Pure silver malate would have given 62.00 per cent silver. In view of 

 the fact that the acid itself was not purified before the silver salt was 

 formed, the analytical results are sufficiently close. Doubtless other 

 acids than malic are present in very small quantity in the crab apple. 

 The significant fact is that the fresh fruit contains malic acid as the pre- 

 dominant acid, and not enough succinic acid so that we were able to 

 isolate it. 



