of a newly 'discovered vegetalle Acid. 443 



Ascertaining this fact, seemed to be infusion of brazil wood al- 

 tered by distilled vinegar ; and with this it even appeared that 

 the solution contained an excess of base. 



Thus it appears, that malic acid never forms with carbonate 

 of lin^e any other than acidulous salts; and, as Scheele ob- 

 serves, these solutions in some days deposit the neutral salt in 

 crystals. But with these carbonates the sorbic acid forms 

 neutral salts, which, as soon as formed, precipitate. 



Scheele ascertained that malate of magnesia is a deliques- 

 cent salt*, and in my trials I could not obtain it in a crystalline 

 form. Wiien evaporated, it became thick, and dried into a 

 semitransparent substance, which softened with the smallest 

 quantity of water, and formed matter of a syrupy consistence. 

 The same earth, heated in sorbic acid, afforded a liquor which, 

 after filtration, deposited permanent crystals in abundance: they 

 required for solution no less than 28 parts of water at 60. f 



The malate of alumina was found by Scheele to be a salt 

 very difficult of solution. I wished to discover the properties 

 of the sorbate. I therefore boiled some very pure alumina that 

 had been just prepared, and was therefore still soft, with sorbic 

 acid: the boiling was continued for almost an hour, and after 

 filtration, I discovered with no small surprise that the alumina 

 had not been acted upon. The acid was tried by every means, 

 and notliing but the most minute vestiges of the earth could be 

 obtained. Thus there is no sorbate of alumina. 



I consider that from this property the sorbic acid may become 

 a valual)le instrument of analysis. The process for separating 

 alumina from other earths has been complicated and uncertain: 

 may it not be rendered simple by the use of this acid, employed 

 in excess ? 



Thus, I think there can be no doubt that the sorbic acid is 

 an acid SJii generis, and probably intermediate between malic 

 and oxalic. With regard to the other acids, with which the st)r- 

 bic coexists in fruits, it is to be observed, that it is never found 

 in mature fruits that contain any other than the malic ; that the 

 latter is never found alone in any mature fruit, but ahva.vs ac- 

 companied by the sorbic; and that these two acids, when toge- 

 ther, exclude all others. To this, however, there is an apparent 

 exception, namely, the berry of the Sambucus vigra, which (pro- 

 bably from the immense quantity of mucilage and colouring 

 matter present) afforded me no sorbic acid. The fruits that 



* Creli's Chem. Annul. 1785. ii. C97. 



t It deserves remark, tliat in Sclieelc's experiments there could have 

 l)een no sorbic acid present, as mij^ht have been expected, had he pre- 

 pared his acid from apples : he obtained it tVora gooseberries, and thereby 

 avoided this source of fallacy. 



contain 



