WHEX tartaric acid in aqiieous solution interacts with certain oxidising agents in presence of a trace of a ferrous salt, a solution is obtaiued which gives a beautiful violet colour on the addition of caustic alkali. I observed this change some years ago, and proposed it as a distinguishing test for tartaric acid. Tartaric and racemic acids are the only substances yet examined which behave in this way, citric, malio, succiuic, o x d i c , and a variety of other acids having been tried with negative results. The soiution t o be examined is mixed with a drop of ferrous sulphate solutiou, follon-ed by a drop of hydrogen pei~oxide, and I hen made alkaline with caustic soda o r potash. Acids destroy the colour, but alkalis restore it. Excess of ferrous salt or of oxidising agent prevents or destroys the effect. It was observed subsequently that the iron may be removed f r o m the acid solution by precipitation with a ferrocyanide ; t h e filtered liquid has very powerful reducing properties, and, with ferric chloride and alkali, gives a violet colour, which is changed to a transient emerald-green bj-dilute miueral acids. The eifects are rery similar to those giveu by ferric chloride with pyrocatechin o r with phloroglucin. Chlorine water, hypochlorites, bayium peroxide, sodium peroxide, or potassium permanganate may be employed as oxidising agents in place of hydrogen dioxide, but the resiilts are not so good. Xitric and nitrous acids are inactive in this respect, as also, apparently, is ozone. If, however, ozonihed air is passed into ether, i t becomes strongly active ; this is, perhaps, due to t h e formation of ethyl peroxide. If moist ferrous tartrate, prepared by precipitation, is exposed to the air for about 10 minutes and then treated with excess of caustic
THE specific influence which ferrous iron exerts on the oxidation of certain hydroxy-acids has been pointed out by one of the authors in several previous communications (Trans., 1894, 65, 899 ; Proc., 1898, h.). I n the case of tartaric acid, for example, two atoms of hydrogen are removed from a molecule of the acid with the production of dihydroxymaleic acid. For the purpose of bringing rtbout this change, the presence of ferrous iron is absolutely essential, but its proportion bears little, if any, relation to the yield of the product, the influence of the iron being apparently of the nature usually described as catalytic.' The most efficient oxidising agent for the purpose is found to be hydrogen dioxide, but a similar result may be obtained by chlorine, potassium permanganate, &c., by electrolysis, and by atmoapherio oxygen in presence of sunlight.The study of this oxidation process is now being extended to ~everaS other hydroxy-acids, and Messrs. Morrell and Cross have undertaken its application to certain carbohydrates. Aiming at a complete investigation of the reaction as regards various typical classes of hydroxycompounds, the present authors are making a series of observations on the behaviour of various akohoh, and this communication deals with the results which have so far been obtained. It will be shown that, in the case of all the polyhydric alcohols examined, the presence of ferrous iron exerts a remarkable influence YOL. LXXV.
THE oxidation of various organic substances by means of hydrogen dioxide and other agents in presence of small quantities of iron salts, has formed the subject of a considerable number of communications to the Society and elsewhere (compare Fenton,
the authors have described the isolation, properties, and constitution of bromomethylfurfural, C6H,0,Br. It was shown that this beautifully crystalline substance results from the action of hydrogen bromide on ketohexoses, such as laevulose and sorbose, or on carbohydrates, which are capable of giving rise to ketohexoses on hydrolysis, such as cane sugar or inulin, and that it may be obtained in a similar manner from various forms of cellulose (Trans., 1901, 79, 361). The bromine in this compound is extremely reactive, so that it may be quantitatively estimated by direct precipitation with silver nitrate in the cold ; the substance itself is hydrolysed by boiling water, in presence of barium 3~2
XLL-The Constitution of a new Dibasic acid, resulting from the Oxidation of Tartaric Acid. By HEKRY J. HORSTMAN FEKTON, M.A. WHEN tartaric acid is oxidised under certain conditions in presence of ferrous iron, a new acid is produced which has powerful reducing properties, and gives beautiful colour reactioiis with ferric salts. The
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