one sixth part of the prussic acid, which is decomposed by the quan- 

 tity of oxygen in the oxide present as a constituent of that salt, and 

 hence five more equal quantities are requisite to effect the complete 

 decomposition of the whole. In all cases it is observable that the 

 quantity of azote produced is exactly equal in volume to the quan- 

 tity of prussic acid gas decomposed, and the quantity of carbonic 

 acid exactly the double of the same measure. Together with these 

 is produced a quantity of water, containing twice as much oxygen as 

 is contained in the carbonic acid. 



The author takes pains to describe, with much precision, the pre- 

 cautions which he found it expedient to employ for effecting the en- 

 tire decomposition of the prussic acid, the mode of preparing the red 

 oxide, of grinding the materials, of charging the tube that he employs) 

 as a retort, of applying the heat to the several parts in succession, and 

 of receiving and examining the products. 



The results of this analysis of prussic acid, show that 

 100 grains consist of 34'8 carbon. 

 40' 7 azote. 

 24'5 hydrogen. 



In a Table which follows, the author exhibits, at one view, the re- 

 sults of his analysis of prussic acid, and of ten different compounds 

 into which it enters ; and at the same time a comparative statement 

 of those proportions which may be supposed more near approximations 

 to the truth, from theoretic considerations of the number of atoms 

 contained in each of the salts under examination. 



On the Nature and Combinations of a newly discovered vegetable Acid ; 

 with Observations on the Malic Acid, and Suggestions on the State 

 in which Acids may have previously existed in Vegetables. By M. 

 Donovan, Esq. Communicated by William Hyde Wollaston, M.D. 

 Sec. R.S. Read June 1, 1815. [Phil. Trans. 1815, p. 231.] 



The acid here noticed by the author being obtained in greatest 

 quantity from the fruit of the Sorbus aucuparia, is denominated by 

 him sorbic acid, in order to distinguish it from other known vegetable 

 acids. To prepare it, he presses the ripe fruit, previously bruised, in 

 a linen bag, and thereby obtains nearly half its weight of juice. 

 With this juice he mixes a solution of acetate of lead, and obtains a 

 precipitate of sorbate of lead, which requires to be frequently washed 

 with cold water. The purified powder is then boiled in a large quan- 

 tity of water, which dissolves a part as a super-sorbate, leaving un- 

 dissolved a sub-sorbate. The liquor being filtered and suffered to 

 cool, deposits brilliant crystals of purified sorbate of lead. 



To the crystals thus obtained he adds a quantity of dilute sulphuric 

 acid, sufficient to separate nearly the whole of the lead ; and having 

 then separated the remainder by a current of sulphuretted hydrogen 

 gas, he obtains the acid in a state of purity. 



The acid to which this bears the nearest resemblance, is the malic ; 

 and indeed these two acids appear to the author to have been con- 



