On the Proteid Reaction of Adamkiewicz, &c. 31 



common to aldehyde-acids, as glycuronic acid, HCO(CH.OH)4COOH, 

 gives wholly negative results. Again, a ketonic acid so closely related 

 to glyoxylic acid as pyruvic acid, CH 3 .CO.COOH, gives no indication 

 of a reaction. 



Glyoxylic acid stands, of course, alone in containing the aldehydic 

 and carboxylic groups in juxtaposition. Our observations are far 

 from being complete enough to enable us to assert that a reaction with 

 proteid of the special type under consideration depends essentially 

 upon this particular structure. But the preliminary observations we 

 have made tend to give some probability to this view. At least it 

 may be said that hitherto we have never obtained a reaction except 

 with products in which either glyoxylic acid has been shown to be 

 present, or in which its presence is extremely probable. 



For instance, we have found that mesoxalic acid (prepared from 

 barium alloxanate) in aqueous solution gives with proteid and sul- 

 phuric acid a perfectly typical Adamkiewicz reaction ; but under the 

 conditions employed we have found that a portion at least of the 

 mesoxalic acid present loses carbon dioxide, so that it is in the highest 

 degree probable that glyoxylic acid is in this case also the substance 

 which reacts. 



Pyruvic acid gives, as we have said, no trace of a reaction, but the 

 product of its oxidation by peroxide of hydrogen undoubtedly reacts. 

 Paralactic acid, itself inactive, yields also an active product on oxida- 

 tion by Fenton's method at the temperature of the water bath. These 

 two cases go together, as Fenton and Jones have shown that lactic acid 

 yields pyruvic acid when oxidised at 0° in the presence of ferrous iron. 

 It seems extremely probable that the oxidation of the pyruvic acid at 

 the higher temperature yields mesoxalic acid, and that the reaction 

 obtained is therefore due in each case to glyoxylic acid. 



One abundant source of a reactive substance is found in the oxida- 

 tion of glycerin by Fenton's method, carried out at the temperature of 

 the water bath. Glyceric acid yields the substance under like condi- 

 tions ; and, as Fenton and Jones* have shown that glyceric acid, when 

 the oxidation is carried out in the cold, gives a product which is almost 

 certainly either hydroxy-pyruvic acid or the tautomeric substance 

 dihydroxyacrylic acid, the facts here quite probably fall into line with 

 those just enumerated. The substance which reacts with proteid is 

 only obtained in quantity in these cases when the oxidation is carried 

 out at higher temperatures than those used by Fenton, and if the 

 oxidised products are distilled, it is always found that the distillate 

 gives the reaction. 



When dextrose solutions are boiled with peroxide in the presence of 

 •ferrous salts a substance is formed, volatile with steam, which yields 



* < Journ. Chem. Soc.,' 1900, vol. 77, p. 72. 



