On the Nature and Comlinatlons of a vegetalle Acid. 433 



would then only collect half the quantity of rain it would have 

 done, had the drops fallen perpendicularly. 



From this explanation it follows, that the best situation for a 

 rain-gage is near the ground, and where it may be well defended 

 from the wind. 



Lynn, Dec. 11, 1815. Ez. WalKER. 



[To be continued.] 



LXXXI. On the Nature and Comh'mations of a newlij -disco- 

 vered vegetable Acid; ivilh Observations on the malic Acid, 

 and Suo-aestions on the State in which Acids may have pre- 

 viously existed in Vegetables. By M. Donovan, Esq. 

 Commimicated by W. H. Wollaston, M.D. Sec. R.S.^ 



Having often observed the sour disagreeable taste of the ber- 

 ries of the Sorlms (or Ptjrus) aucuparia, it occurred to me that 

 the juice might contain an acid of a peculiar nature, and 1 re- 

 solved to submit it to a strict examination. I was not at that 

 time acquainted with the fact, that these berries had already 

 occupied the attention of Scheele, and that this philosopher had 

 pronounced their acid to be the malic. 



Some preliminary experiments showed me that the juice oc- 

 casioned a precipitation in acetate of lead and nitrate of silver; 

 but it produced no change in lime-water, barytes-water, sul- 

 phate of copper, nor, although it might be expected from its 

 very astringent taste, did it affect sulphate of iron. 



A quantUv of the juice was poured into a solution of sugar of 

 lead: a curdy and somewhat heavy precipitate appeared, which 

 was separated bv filtration : this, from its solubility in acetic and 

 dilute nitric acid, I judtred to be malate of lead. 1 he filtered 

 liquor wa.s red, and perfectly transparent ; but after a few hours 

 I observed a powder deposited at the bottom, and as I saw no 

 sufficient reason for its appearance, it attracted my attention. 

 To the naked eve it looked like a coarse powder ; but, when 

 examined by the microscope, proved to be composed of amor- 

 phous crvstklline grains. With this small quantity of powder 1 

 made some trials,^ which ended in exciting further curiosity. It 

 was probable, that the precipitate which remained on the filter 

 might be made to furnish more grains, and accordingly, after 

 edulcorating the mass, I caused boiling water to pass through 

 it. After two hours I examined the different washings ; those 

 made with cold water remained as at first, but those with boiling 



* From tlic I'liilosopliical Transactions for 1815, part ii. 

 Vol. 46. No. 212. Dec. 1815. E e vvater 



