Mr. Everitt on Garden Rhubarb as a Source of Malic Acid. 327 



for September 2, 1843, in which the writer attempts to appro- 

 priate my views, I do not know of any observations to which 

 the Professor can allude, but those which I published in your 

 Journal for March 1839 [S. 3. vol. xiv. p. 174], and if he will 

 refer to them he will perceive that he has not quite under- 

 stood my notions. My experiments were made with elastic 

 and not muscular tissue, and the increase of heat in the 

 caoutchouc operated on was observed immediately after it 

 had been elongated and before it had been allowed to re- 

 contract. 



As the Professor's imperfect explanation of my views might 

 bring them into some discredit, I shall feel obliged by your 

 publishing this Note. 



I have the honour to be, Gentlemen, 



Your obedient Servant, 



J. M. Winn. 



Truro, Sept. 21, 1843. 



XL. The Leaf-stalks of Garden Rhubarb as a Source of 

 Malic Acid. By Thomas Everitt, Esq.* 



THE large quantity of this substance which is brought to 

 our vegetable markets for several months in the year, 

 beginning very early in spring, and its powerful though 

 agreeable acid taste, make it a subject worthy of a more minute 

 chemical examination than any which it has as yet been sub- 

 jected to. 



The leaf-stalks of garden rhubarb were first examined by 

 Mr. Hendersonf, who discovered in them, as he thought, a 

 peculiar acid; afterwards by M. LassaigneJ, who showed 

 that the supposed new acid was oxalic acid. But these expe- 

 rimenters examined only the precipitate obtained by putting 

 chalk into the expressed juice; the first-named decomposing 

 the insoluble precipitate thus obtained by sulphuric acid; the 

 other, by boiling it with excess of carbonate of potassa, then 

 neutralizing the solution with nitric acid, and precipitating by a 

 salt of lead, decomposing the latter by sulphuretted hydrogen, 

 and thus getting crystals which were oxalic acid. Now by 

 both these processes, those chemists threw away, in the liquid 

 which floated above the oxalate of lime, an important con- 

 stituent in a large quantity, viz, malate of lime, with a great 

 many other things of less importance, but which rendered the 



* Communicated by the Chemical Society; having been read February 

 7, 1843. 

 f Thomson's Annals of Philosophy, vol. viii. p. 247. (1816.) 

 % Annalet de Chimie et de Physique, torn. viii. p. 402. (1818.) 



