C 469 ) 

 LXXXIV. Proceedings of Learned Societies. 



ROYAL SOCIETV. 



June 1 . J. HE conclusion of Mr. Donovan's paper on the 

 ^Derries of the mountain ash or roan-tree, the Sorbus aucuparia 

 of Linnaeus, was read. In the series of ingenious experiments 

 devised by the author, on apples, pears, crabs, and roanberries, 

 he discovered the existence of a new and peculiar acid in the 

 latter, which he calls sorbic acid. The roanberries, although an 

 object of vulgar superstition in all the northern countries of 

 Europe, in which they have been deemed an antidote against 

 witchcraft, and of a very peculiar taste, have never been sub- 

 mitted to any chemical analysis, since Scheele discovered in 

 them and other vegetables the existence of malic and citrie 

 acids. Some experiments have indeed been made on malic acid 

 by Vauquelin and Proust, but our knowledge of this and many 

 other vegetable acids is still very imperfect. The researches 

 and discoveries of Mr. Donovan will doubtless attract the at- 

 tention of chemists to these substances. In preparing the sorbic 

 acid Mr. D. pursued the method of Scheele as improved by 

 Vauquelin ; he expressed the juice of the ripe berries, boiled it 

 saturated with carbonate of potash, and added acetate of lead, 

 which was precipitated in the state of a compound salt contain- 

 ing malat of leadi the latter was again precipitated, and the 

 sorbic acid obtained pure. The author related a great number 

 of experiments on roanberries and apples, to ascertain the rela- 

 tive quantities of acid which thev contain : he found that the 

 sorbus berries yield nearly one-half their weight of juice, con- 

 sisting of sorbic and malic acids, the former of whicli was much 

 more abundant, — but that apples contain a very small proportion 

 of sorbic acid, and that plums, pears, &c. have none. The dif- 

 ference between the salts formed by these acids is very striking j 

 the sorbats of potash, soda ox ammonia are crystallized salts, so- 

 luble in water but not in alcohol ; the malats., on the contrary, 

 are not crystallizable, are deliquescent, and slightly soluble in al- 

 cohol. Mr. D. also tried several experiments on otlver sub- 

 stances, and found that there is no sorbat of alumina : this fact 

 will facilitate the complex analysis of many minerals containing 

 alumina, which have hitherto occasioned the appearances of 

 .some anomalies which do not exist in nature. The author then 

 proceeded to offer some original conjectures on the composition 

 of vegetables in general, and what has been called the liitter 

 principle in particular : the substance which communicates a 

 bitter sensation he considers as the matrix or radical of the malic 

 *iud sorbic acids. He seemed to think that these acids may 

 G g 3 rather 



