440 On the Nature and Comlinations 



white brilliant flake of a silver lustre, resembling well-prepared 

 acetate of mercury, but still more beautiful. 



As to the iiniorphous crystalline grains which first attracted 

 my attention, the following experiment elucidates the theory of 

 their formation. A quantity of the pure acid obtained bv the above 

 process, was boiled for some time on an excess of carbonate 

 of magnesia. The liquor after filtration was found to restore 

 the original colour of reddened litnnis, and to render green the 

 tincture of cabbage. An acetate of lead was formed by boiling 

 solution of super-acetate on carbonate of lead. This solution 

 was mixed with the former, and the precipitate was collected by 

 the filter. 



Notwithstanding the evident excess of magnesia existing in 

 one solution, and the necessary neutrality of the other, yet the 

 filtered liquor was found strongly to redden litmus paper. We 

 are not to suppose that the two salts evolved a free acid during 

 their mutual decomposition. As much oxide of lead was li- 

 berated from the acetate, as was necessary to the neutrality of 

 the acid eliminated from the compound with magnesia ; the so- 

 lution would therefore have retained all its ingredients in a state 

 of neutrality, except that which originally contained an excess 

 of magnesia. But the new salt of lead, at the moment of its 

 formation, was decomposed by the water present into a super- 

 and a sub-salt ; the excess of acid being not only sufficient to 

 saturate the redundant magnesia, but also to leave a portion free 

 in the solution. This liquor, after an hour, deposited a quantity 

 of crystalline grains, and after that, the acidity increased. 

 Hence appears the reason of a crvstallization in the original li- 

 quor : a super-salt is formed, which after a while deposits the 

 neutral salt in a crystalline form. 



This acid appearing, from what has been alreadv stated as 

 well as from what will be hereafter detailed, to be of a peculiar 

 nature, it became necessary to give it a name. After some con- 

 sideration I bestowed on it one, which, although not unexcep- 

 tionable, is sufficiently accordant with the general analogy of 

 chemical nomenclature, and wliich has received the approbation 

 of some competent judges. Until a better name be devised, I 

 have called it the Sorbic acid. 



To establish its peculiar nature, I have examined its combi- 

 nations witli certain bases, but have confined myself to those 

 of which the analogous combinations amongst the malates had 

 been already examined by Scheeie. The sorbic and malic acids 

 not having been distinguished by that philosopher, it seemed 

 that here the distinction ought particularly to be established: 

 and the standard of comparison must necessarily be whatever 

 had been ascertained of the malates by their discoverer. 



Sorbic 



