380 Royal Society : — 



The acid oil of the mouiitaiu-ash berry exhibits a very remarkable 

 deportment with the alkalies and acids. When gently heated (a 

 temperature of 1 00° is sufficient) with solid hydrate of potassa, or 

 when boiled with concentrated hydrochloric or moderately dilute 

 sulphuric acid, the oil is readily converted into a s[)lcndid crystalline 

 acid, greatly resembling benzoic acid in its general characters, which 

 has the same composition as the oil itself. I have established this 

 remarkable isomerism both by careful observation of the conditions 

 of transformation, and by the analysis of the crystalline acid as well 

 as of some of its salts and derivatives. I propose to designate this 

 new compound by the term sorbic acid, thus reviving an old name 

 which had at one time been used for malic acid. The isomeric oil 

 obtained by distilling the juice of the mouutain-ash berry, the acid 

 properties of which are much less pronounced, may then be called 

 Parasorbic acid. 



Sorbic acid. — This substance is readily soluble in alcohol and 

 ether, less so in water. Heated with a quantity of water insuffi- 

 cient for solution, it fuses ; the aqueous solution, saturated by ebul- 

 lition, solidifies on cooling into a netvt'ork of interlaced needles. The 

 acid crystallizes best from a mixture of alcohol and water, in which 

 the latter predominates ; from this solvent it is often deposited in 

 magnificent needles several inches in length. Sorbic acid fuses at 

 134°'5. It boils at a much higher temperature, and may be volati- 

 lized without decomposition. 



The alkaline sorbates are all soluble in water, the potassium, 

 sodium, and ammoinum compounds are extremely soluble, and cry- 

 stallize with difficulty ; the barium and calcium salts are less soluble, 

 and may be obtained in splendid scaly crystals of the lustre of silver. 

 Their crystallization is facilitated by the addition of a small quantity 

 of alcohol. Both salts are anhydrous, their analysis agreeing with 

 the formulae 



Sorbate of barium C,_. [IL Ba] O, 



Sorbate of calcium .... C,.j [H, Ca] O^. 



The silver-salt is a white amorphous precipitate, extremely inso- 

 luble in water, readily obtained by the decomposition of the ammo- 

 nium compound by nitrate of silver. Both combustion and silver- 

 determination proved this salt to be 



Sorbate of silver Cj, [H. AgJO^. 



The ether of sorbic acid is readily procured by treatment of the 

 alcoholic solution of sorbic acid with hydrochloric acid, or by the 

 action of chloride of sorbyle upon alcohol. It is a colourless liquid 

 of an agreeable aromatic odour resembling that of benzoic ether, 

 boiling at 191° C, and containing: — 



Sorbate of ethyle C,„ H^, 0,=C,, [H,(C, H3)]0,. 



The experiments which I have quoted are sufficient to fix the 

 composition of sorbic acid. I have nevertheless produced some 

 additional derivatives of the acid. 



Chloride of sorbyle is obtained by the usual processes ; by the 



