[ 379 ] 

 LX. Proceedings of Learned Societies. 



ROYAL SOCIETY. 



[Continued from p. 308. J 



March 10, 1859. (Sir Benjamin C. Brodie, Bart., Pres., in the Chair.) 



THE following communications were read : — 

 " New A^olatile Organic Acids, from tlie Berry of the Moun- 

 tain Ash." By A. W. Hofmann, LL.D., F.R.S. 



Whoever has been engaged in the preparation of malic acid from 

 the juice of the unripe berries of the Mountain Ash {Sorbus Aucii- 

 paria), cannot have failed to perceive the peculiar powerful odour 

 evolved during the evaporation of the liquid partially saturated with 

 lime. The body to which this odour belongs was hitherto un- 

 known, and only lately, my friend and former pupil, Dr. George 

 Merck of Darmstadt, when preparing malic acid on a large scale, 

 conceived the happy idea of evaporating the liquid in a distilling 

 apparatus. He thus obtained an acid distillate, from which he suc- 

 ceeded in separating an oily bodj^ possessed of acid properties. To 

 the kindness of Dr. Merck I am indebted for an appreciable quan- 

 tity of this remarkable body, which has enabled me to examine its 

 properties and establish its composition. 



The preparation of the oil from the aqueous acid obtained by 

 distilling the mother-liquor of the bimalate of calcium, presents no 

 difficulty. The liquid is saturated with soda, evaporated and mixed 

 with dilute sulphuric acid, when the oil rises as a brown layer to the 

 surface of the liquid. It is separated by ether, and after the volati- 

 lization of the latter, submitted to distillation. The first portions 

 of the distillate contain appreciable quantities of water; the thermo- 

 meter, however, rapidly rises above 200° C. What now distils is a 

 perfectly pure compound, which, on redistillation, exhibits a con- 

 stant boiling-point at 220° C. Freshly distilled, the oil is colourless, 

 but it soon acquires a yellowish tint. It has a peculiar aromatic 

 odour, not disagreeable when dilute, but rather offensive when con- 

 centrated. The specific gravity is 1"0681. It is somewhat soluble 

 in water, very soluble in alcohol and ether ; these solutions are di- 

 stinctly acid. The oil dissolves in potassa and ammonia, also in the 

 carbonated alkalies, without, however, expelling their carbonic acid. 

 Mineral acids separate it again from these compounds. 



The analysis of the oil shows that it contains carbon, hydrogen, 

 and oxygen in the ratio of 



CaH^O; 



but the determination of the silver in a white amorphous silver com- 

 pound, obtained by adding nitrate of silver to the ammoniacal solu- 

 tion of the oil, shows that this expression must be quadrupled, and 

 that the acid and silver-salt are represented by the following 

 formulae : — 



Acid . . C,,II,0, 



Silver-salt C,,; [II, Ag]0.. 



