On the Proteid Reaction of Adamhievncz, &c. 



especial care to keep the mixture at 0°, and without attempting to 

 .separate the dioxymaleic acid formed. A little of the oxidised solution 

 was heated direct on the water bath till all evolution of C0 2 had 

 ■ceased, and then cooled. A trace of Witte's peptone was added to the 

 solution, which was free from excess of peroxide, and then strong 

 sulphuric acid. An intense colour reaction was obtained exactly 

 similar to that seen in a normal Adamkiewicz reaction when carried 

 out with acetic acicl rich in the chromogenic substance. The solution 

 .gave also in the spectroscope an exactly similar absorption band. 



We found subsequently, however, that glycollic aldehyde, isolated, 

 either in the syrupy or crystalline condition,* and whether in aqueous 

 or acetic acid solution, gave no colour reaction under like conditions, 

 but yielded only a charred product when the sulphuric acid was added. 

 Moreover, acetic acid, however rich in the chromogenic substance, 

 aiever reduces (after neutralising) alkaline copper solutions. A reduc- 

 tion of ammoniacal silver solutions may be obtained, but never any 

 ■effect upon Fehling's solution. 



We came to the conclusion, therefore, that the substance sought 

 must be an oxidation product of glycollic aldehyde ; and we now 

 found that the latter needs only to be treated by Fenton's oxidation 

 method carried out at the temperature of the water bath to give a 

 product, which, when free from excess of peroxide, yields in acetic or 

 .aqueous solution the proteid reaction abundantly. 



At this time we made another observation of the greatest assistance 

 to our inquiry, finding that the chromogenic substance is produced in 

 abundance when oxalic acid is reduced in aqueous solution by means 

 -of zinc and sulphuric acid, or, more conveniently, by sodium amalgam. 



The reduction need last for a few minutes only, and a little of the 

 solution, without further treatment, will then be found to give an 

 intense colour with proteid and sulphuric acid, the product showing 

 spectroscopic appearances identical with those of the ordinary Adam- 

 kiewicz reaction. 



There was now no doubt that a colour reaction, not to be dis- 

 tinguished from that of Adamkiewicz, is yielded by a substance which 

 is at once an oxidation product of glycollic aldehyde and a reduction 

 product of oxalic acid. It was difficult to see how this substance could 

 be other than glycollic acid, glyoxylic acid, or glyoxal. 



Pure glycollic acid was obtained from Merck. It gave no trace of a 

 •colour reaction with proteid solution and sulphuric acid. The product 

 of its oxidation by Fenton's method reacted, however, in a perfectly 

 typical manner, and Fenton and Jones have found that this product is 

 glyoxylic acid. 



The latter was therefore prepared from alcohol by the method of 



* Fenton and Jackson, ' Journ. Chem. Soc.,' vol. 75, p. 575, 1899. We were 

 indebted to Mr. Hy. Jackson for a supply of the crystalline aldehyde. 



