The determination of boric acid in cider, fruits, etc.

Abstract

THE natural occurrence of traces of boric acid in certain plants, trees, fruits, etc., has been pointed out by various observers,* and the presence of this acid in wine, cider, and allied products follows as a natural consequence. These facts were confirmed at the outset of our experiments upon the presence of preservatives in cider. All the eiders examined were found to contain a small but distinct amount of boric acid, and st similar result was obtained .by the examination of various fruits, such as apples, pears, quinces, grapes, and pomegranates. Hence boric acid in cider, Perry, wine, etc., cannot be regarded as an adulteration unless the amount ig materially greater than can be fairly ascribed to natural causes. Our experiments have been chiefly made on cider and apples, and the following observations have special reference to these substances.The detection of boric acid in cider and fruits can be readily effected by evaporating 20 C.C. of cider or apple-juice to dryness and igniting the residue, or by directly igniting 25 grsmmes of apple or other fruit. The ash is rendered distinctly acid to litmus with dilute hydrochloric acid, a piece of turmeric paper partially immersed in the liquid, and the whole evaporated to dryness on the water-bath in a flat porcelain dish. The residue is further dried in the water-oven for a short time. In the presence of boric acid the turmeric paper will acquire a brownish-red colour, which, on being moistened with a drop of caustic soda solution, is changed into a variety of colours, chiefly green and purple,The quantitative determination of boric acid in cider and fruits, etc., we have found very troublesome, and this has been the subject of numerous experiments.The English references only are given : Boric acid in trees and lants, E. Bcchi, J. C. S., lviii., 656 ; J. C. S. I., ix., 635 ; in hops and (therefore) beer, but not in mart or barley, J. Brand, ASALYST, xviii., 135 ; in all parts of the vine, Baumert, Rising (reference not known) ; in peach-trees and peaches, Knorr (reference not known) ; in grapes and wine, apples, pears, radishes and lettuce, M. Gassend, Phurm. Journ., xxiii., 6 ; J. C. S., lxii., 93 ; in various fruits, A. Hebebrand, ANALYST, 1903, xsviii., 37 ; in fruits generally, E. Hotter, J. C. S., 1890, lviii., 1338 ; in the ash of fruits and vine-leaves, H. Jay, J. C. S., lxx., ii., 327 ; in wine, water-melon, etc., C. A. Crampton, J. S. C. I., viii., 569 ; in wines, cider, perr and fruits, day and Dupasquier, J. C. S., lxx., ii., 76, 327 ; absent from-natural wines, Villicrs and %ayolle, J. C. S., lxx., ii., 75.* The following is a summary of the chief papers on this subject.

Control of Early Blight Fungus (Alternaria alternata) in Tomato by Boric and Phenylboronic Acid

“…One such chemical may be phenylboronic acid (PBA), a phenyl derivative of medicinally important boric acid (BA) [1,2]. Among other sources, boric acid can be found in plants, including almost all fruits [3]. Phenylboronic acid is a commercially available and pharmaceutically acceptable substance [4] that in certain concentrations has a fungicidal effect on several species of human fungi [5], is not toxic to the environment [6] and mammals [7] and has an antitumor effect [7].…”