Page:Proceedings of the Royal Society of London Vol 2.djvu/54

Rh one sixth part of the prussic acid, which is decomposed by the quantity 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 quantity 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 precautions which he found it expedient to employ for effecting the entire 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

In a Table which follows, the author exhibits, at one view, the results 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. 



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 quantity of water, which dissolves a part as a super-sorbate, leaving undissolved 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