505 



matter, which is not always of the same nature. It remains 

 to examine, with more care than has hitherto been clone, the 

 numerous variety of impure acids which have been comprised 

 in a great number of analyses, under the name of malic acid ; 

 it is probable that we will find in them sorbic acid, and perhaps 

 some other new acids masked by this mucous principle. I am at 

 present satisfied in the conviction of the complex nature of the 

 malic acid obtained from the principal substances in which it 

 is indicated, as apples, houseleek, sorbus berries, and grapes.' 

 Elsewhere (p. 150) he says that the malic acid of Scheele con- 

 tains abundant foreign matter, ' which completely masks all its 

 properties.' From this extract we may infer it to be the opi- 

 nion of Braconnot that sorbic acid is a different substance from 

 the malic acid of Scheele, and that the latter should not be 

 considered as a distinct acid, inasmuch as it is a compound of 

 an acid with a large quantity of another vegetable proximate 

 principle ; and we know that both are combined by so power- 

 ful an aflSnity that difficult processes are necessary for their 

 separation. 



« In my paper, published in the Philosophical Transac- 

 tions, I laid claim to the discovery of a new vegetable acid, 

 possessing properties and forming combinations quite different 

 from those of Scheele's acid. That I established my claim was 

 not disputed, either professedly or incidentally by the subse- 

 quent researches of Braconnot or Vauquelin. The difference 

 between Scheele's acid and mine is so great that each was 

 deemed sui generis until Braconnot's discovery of the mucous 

 disguise. Scheele represented his malate of lead as a precipi- 

 tate ; the sorbate of lead consists of strikingly beautiful crys- 

 tals : his malate of potash, malate of soda, and malate of am- 

 monia, are all uncrystallizable and deliquescent ; the sorbates 

 of these bases are all capable of furnishing crystals which do 

 not deliquesce : his malate of magnesia is a deliquescent mass; 

 but sorbate of magnesia is a crystallizable salt which is perma- 

 nent in the air. Thus none of the malates, as described by 



2 p 2 



