26 



Messrs. F. G. Hopkins and S. W. Cole. 



Debus. The calcium glyoxylate first obtained was recrystallised 

 thrice. A minute crystal of the salt dissolved in water, together with 

 a little proteid, gave, upon the addition of strong sulphuric acid, a 

 vivid colour reaction not to be distinguished, spectroscopically or other- 

 wise, from the reaction of Adamkiewicz. 



Glyoxal, prepared subsequently from the products of the same 

 Debus oxidation, gave no trace of such a reaction.* When glyoxylic 

 acid is added to glacial acetic acid, previously deprived of its chromo- 

 genic power by distillation, further distillation now yields a distillate 

 which reacts typically, and the glyoxylic acid comes over charac- 

 teristically, like the original chromogenic substance in the earlier 

 fractions. 



III. GlyoxAjlic Acid from Acetic Acid. 



It now became necessary to ascertain whether glyoxylic acid is, as a 

 matter of fact, present in such specimens of acetic acid as yield the 

 Adamkiewicz reaction. 



In seeking for evidence as to this, it was necessary to remember that 

 exceedingly little glyoxylic acid is necessary f o the reaction. With an 

 aqueous solution of such strength as will give no more than an 

 opalescence with phenyl hydrazine, the colour reaction with proteid is 

 well marked. 



It was found, however, that oxidation with hydrogen peroxide 

 confers abundant chromogenic power upon acetic acid previously giving 

 no proteid reaction ; and it was our first endeavour to ascertain whether, 

 as a result of this, glyoxylic acid is produced in quantity sufficient for 

 its easier identification. 



The presence of small quantities of ferrous iron accelerates the 

 oxidation, and is, perhaps, essential to it. t The process occurs most 

 rapidly at boiling temperature, and proceeds most satisfactorily when 

 the acetic acid is repeatedly distilled with the peroxide. The limit of 

 the oxidation is in any case soon reached. Using twenty volumes 

 strength, the peroxide is found to be rapidly destroyed till a volume 

 has been added about equal to that of the acetic acid taken ; after this 

 the reaction becomes very slow. 



We proceeded as follows : — A litre of glacial acetic acid was mixed 

 with an equal bulk of twenty-volume peroxide and some ammonio 

 ferrous sulphate added (half a gramme per litre, Or less). The mixture 



* Many specimens of commercial glyoxal give the reaction, but only, as we 

 have found, when they contain gljoxylic acid ; preparations of glycollic acid may 

 contain traces of the latter. 



f We have found that some specimens of peroxide bring about the oxidation 

 without the addition of iron ; others undoubtedly act much less readily, unless a 

 ferrous salt is added. While we have been unable to detect the presence of iron 

 in the former, so small a quantity appears to affect the reaction that it is possible a 

 trace of the metal present as an impurity may account for the difference. 



