Oct 23, 1921 Acids of Pyrus coronaria, Rhus glabra, Etc. 225 



was to treat the juice with lead acetate, which supposedly threw out all 

 iodin-absorbing compounds except the succinic acid glucosid. Then the 

 presence of the latter, which was never isolated at all, was inferred from 

 two circumstances: (i) that the purified juice absorbed iodin, and (2) 

 that, after the absorption of iodin, a precipitate could be obtained with 

 basic lead acetate, supposed to be lead monoiodosuccinate, which when 

 treated with a mineral acid to liberate the free monoiodosuccinic acid, 

 and then with finely divided metallic silver, gave malic acid. The pro- 

 duction, under these circumstances, of malic instead of tartaric acid was 

 thought to indicate that iodosuccinic acid had been present rather than an 

 iodin derivative of the widely distributed malic acid. 



The weakness of the whole argument is sufficiently obvious without 

 going into detail, since neither the putative glucosid of succinic acid nor 

 the iodosuccinic acid was isolated; and it was not shown that the basic 

 lead acetate precipitate was free from lead malate, which one would 

 naturally expect to be found there. To the physiologist who is interested 

 in the ripening of fruits it will be clear that the whole problem of the dis- 

 tribution and significance in metabolism of succinic acid is much in need 

 of more study. Especially, there can be no doubt that Buignet's iodin- 

 absorbing compound (4), whatever it may be, should be taken account 

 of in studies of fruit ripening. It exists in large amount in the unripe 

 fruit and disappears as ripening proceeds. As far as we are aware, it is 

 not even referred to in the recent literature of the subject. 



ACIDS OF RHUS GLABRA 



The acid of the sour, red pericarp of the sumacs (several species related 

 to Rhus glabra) has been variously reported by different investigators as 

 citric, malic, and tartaric. Gallic acid has likewise been reported. 

 The closely related species of true sumacs are doubtless alike as to acid 

 content. Our work, confined to R. glabra, has verified the findings of 

 Rogers {12) nearly a century ago, and Frankforter and Martin (9) that 

 the fruit acid is malic, nearly all in the form of the acid calcium salt. 

 We were also able to isolate free gallic acid, which seems not to have 

 been reported from this particular species. There are statements in the 

 older literature that free gallic acid occurs in the leaves of the European 

 sumac, R. coriaria L. 



The berries of Rhus glabra were boiled with successive quantities of 

 distilled water. The water solutions were clarified and largely freed 

 from tannin by boiling with hide powder and o^gg albumen, and were then 

 shaken with ether. The combined ether extracts were evaporated to a 

 sirupy consistence and deposited gallic acid as a yellow powder. The 

 latter was filtered off on a Buchner funnel and crystallized repeatedly 

 from water. It was obtained in pure and almost colorless condition by 

 precipitation from solution in absolute alcohol by chloroform, or by 

 recrystallization from glacial acetic acid. As obtained by crystallization 



