glyoxalic acid from oxalic

A NOTE ON THE PREPARATION OF GLYOXYLIC ACID AS A REAGENT.

BY STANLEY R. BENEDICT.

(From the Shefield Laboratory of Physiological Chemistry, Yale University.)

(Received for publication, January 5, agog.)

Hopkins and Cole have proposed the employment of a solution of glyoxylic acid as a substitute for the glacial acetic acid used in the Adamkiewicz reaction for the tryptophane grouping in protein or other substances. In the preparation of their reagent, Hopkins and Cole advise the reduction of oxalic acid to glyoxylic, by means of sodium amalgam. Inasmuch as sodium amalgam is not always readily available, it may be of interest to call atten- tion to the fact that metallic magnesium may be employed as the reducing agent for obtaining glyoxylic acid from oxalic acid. The following is the procedure. Ten grams of powdered mag- nesium2 are placed in a large beaker, or preferably a large Erlen- meyer flask, and shaken up with enough distilled water to liber- ally cover the magnesium. Two hundred and fifty cubic centi- meters of a cold, saturated solution of oxalic acid are nowadded slowly. The reaction proceeds very rapidly and with the liber- ation of much heat, so that the flask should best be cooled under the tap during the addition of the acid. The contents of the flask are shaken after the addition of the last portion of the acid and then poured upon a filter, to remove the insoluble magnesium oxalate. A little wash water is poured through the filter, the filtrate acidified with acetic acid3 and made up to one liter with distilled water. The solution gives no reaction for oxalate with

* Hopkins and Cole: Proc. Roy. Sot. Ixviii, p. ar, rgor; also Journal of Physiology, xxvii, p. 418, rgoz, footnote.

2 Magnesium ribbon may also be employed, but in this case the reaction goes more slowly and may be accelerated by warming.

s The reason for the addition of the acetic acid is that the filtrate may sometimes be faintly alkaline in reaction, and in such cases the magnesium would be partially precipitated upon long standing, unless the acid is added.

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52 Preparation of Glyoxylic Acid

calcium and contains apparently only the magnesium salt of glyoxylic acid. This reagent gives very beautifully the char- acteristic reactions for glyoxylic acid.

1 The magnesium could readily be removed, but there appears to be no objection to its presence.

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Stanley R. Benedict

GLYOXYLIC ACID AS A REAGENTA NOTE ON THE PREPARATION OFARTICLE:

1909, 6:51-52.J. Biol. Chem.

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