170 Biographical Account of [Sbpt. 



earthy salt remained behind. In a subsequent paper he gave a list 

 of a considerable number of vegetable substances, chiefly employed 

 in medicine, from which he extracted the same oxalate. 



25. His next djscovcry was the analysis of the salt of wood 

 sorrel, well known in this country under the name of essential salt 

 of lemons. He shewed it to be a salt composed of oxalic acid and 

 potash. It owes its acid qualities to the quantity of acid which it 

 contains. It is a binoxalate. 



2(>. In 1780 he published a dissertation on the separation of 

 magnesia from Epsom salt. When common salt and sulphate of 

 mairi esia are mixed, a double decomposition takes place ; and if 

 the liquid be set aside for some days in winter, when the thermo- 

 meter is below the freezing point, the sulphate of soda crystallizes, 

 and may be separated, after which the magnesia may be precipi- 

 tated in the usual way by an alkaline carbonate. 



-J. The same year he demonstrated that the siderite, or supposed 

 new metal extracted by Bergman from cold short iron, was phos- 

 phuivt of iron ; and that Proust's perlated salt, extracted from 

 Brine, was phosphate of soda. 



28. His experiments on the acid contained in fruits and berries, 

 publi.-hed likewise in 17&5, contains a vast number of new facts. 

 He points out the method of procuring malic acid, and determines 

 its properties. Some fruits, as cranberries, whortleberries, bird- 

 chenies, and the berries of night-shade, contain only citric acid; 

 some, as barberries, elderberries, sloes, serviceberries, plums, con- 

 tain only malic acid ; while others, as gooseberries, currants, bil- 

 berries, cherries, strawberries, cloudberries, raspberries, contain 

 nearly equal quantities of both acids. In the same dissertation he 

 showed that malic acid is formed when sugar is treated with nitric 

 acid at the same time with the oxalic acid ; that gum, sugar of 

 milk, starch, and many other substances, yield both acids when 

 digested in nitric acid. In short, this most valuable paper contains 

 almost every thing relating to the vegetable acids, which was after- 

 wards spread out by Fourcroy, and some other chemists, with so 

 much pan.de, as if they had been novelties discovered by them- 

 selves. 



29. The last paper which Mr. Scheele published, as far as I 

 know, contains his discovery of gallic acid. Unless my memory 

 deceives me, fori have it not in my power at present to consult the 

 original, it made its appearance in 17^6', and not till after the death 

 of the author. He had set aside an infusion of nutgalls for some 

 time in an open vessel. Crystals formed at the bottom of the vessel. 

 These he separated and examined, and found them to consist of a 

 peculiar acid, to which the name gallic acid has been given, the 

 properties of which he describes. 



Such, omitting a few controversial papers, and some letters to 

 Crell of minor importance, is a list of Scheele's writings and dis- 

 coverie , as far as 1 am acquainted with them. Though far from a 

 voluminous writer, his discoveries, both in point of number and 



