Determination of Malic Acid.

Abstract

The method described herein is based on the fact first observed by Walden r that under certain conditions uranium salts produced a very marked increase in the specific rotation of Z-malic acid. Walden noticed that a similar but less marked effect is produced by uranium salts on^-tartaric acid, d-methyl tartrate, Z-quinic, and Z-mandelic acids, the increased rotation being in the same direction as the rotation of the aqueous solution of the substance. He concluded that the effect is limited to the active oxy-acids. As stated by Walden, the requisites of an agent which is to be used for the detection of malic acid by optical means are: (1) That the direction of rotation shall be constant, and (2) that the increase in rotation shall be as large as possible. This, of course, applies also to the quantitative estimation of malic acid. In addition, the agent in question should have little or no influence on any other substances which may occur in conjunction with malic acid. It has long been known that certain substances such as the oxygen compounds of boron 2 arsenic, antimony, molybdenum, and tungsten 3 have the power of increasing the specific rotation of the oxy-acids. Uranium salts, however, are the only ones which fulfill the requirements just stated with any degree of satisfaction. tion of Malic Acid and Its Application in Cane and Maple Products.'' 4 This paper was presented at the forty-second meeting of

Chemical and Physical Development of the Pineapple Fruit II. Carbohydrate and Acid Constituents

“…the dehydration with acetic anhydride was carried out at 100°C for 40 min, and the trichloroacetic acid was omitted. Malic acid was determined by optical rotation of its many1 complex (Dunbar and Bacon, 1911) without prior separation of the acids on ion-exchange columns.…”

Role of Ether Soluble Organic Acids in the Cationanion Balance in Plants

“…The material was then placed in a stout muslin cloth, subjected to 10,000 pounds pressure per square inch in a Carver hydraulic press, and the juice collected. (1)(2)(3)(4)(5)(6)(7)(8)(9)(10), dried in an oven at 950 C., then placed in a muffle furnace and ashed 4 hours at 6000 C. The sulphuric acid was necessary to avoid explosion of the material while ashing.…”

Chemical investigations of the tobacco plant. IV, The effect of the curing process on the organic acids of tobacco leaves

“…Malic acid can be determined in the absence of other optically active substances from the rotation of the uranyl complex according to the method outlined by Dunbar and Bacon (4). Samples (usually 25 cc.)…”