On the Proteid Reaction of AdamMewicz, &e. 



29 



being separated from the associated acetate and isolated in substance. 

 The ease with which the salt dissociates and the volatility of the acicl 

 with water vapour make concentration of small avail. 



The evidence for the formation of glyoxylic acid during oxidation 

 appears, however, to be conclusive, and it is interesting to note that, 

 judging from the gradual development of the reaction with proteid, 

 this oxidation goes on slowly when acetic acid is exposed to air, and 

 especially under the influence of light. Ferrous iron undoubtedly 

 accelerates this, and if acetic acid giving no proteid reaction be some- 

 what diluted, and a little ferrous salt added, exposure to direct sun- 

 light will confer a reactive power in the course of a few hours. 



We have not been able to separate the hydrazone in quantity suffi- 

 cient for its identification from average specimens of untreated acetic 

 acid ; but it appears equally difficult to do so when small quantities of 

 glyoxylic acid, sufficient to confer an average chromogenic power, have 

 been added to a specimen previously giving no reaction. 



On one occasion we obtained a quantity of glacial acid giving the 

 reaction with special intensity. This acid had crystallised in bulk, and 

 we were supplied, with drainings from the crystals. Seven litres were 

 fractionally distilled until the chromogenic substance was concen- 

 trated into about 1 litre. This was nearly neutralised and again dis- 

 tilled. Phenylhydrazine acetate added to the distillate gave a con- 

 siderable quantity of crystalline precipitate, yellow at first, darkening 

 on standing. This was obtained before we had identified glyoxylic 

 acid as the substance sought, and most of the hydrazone was lost in 

 preliminary solubility tests. A small quantity was reserved, however, 

 and this, recrystallised thrice from hot water, melted sharply at 137°. 



The observations we have hitherto made give no quantitative indica- 

 tions of any value. In this paper we have been mainly concerned with 

 the endeavour to prove the nature of the active substance in the 

 proteid reaction. We propose to study the oxidation of aGetic acid 

 further, and to define if possible the conditions necessary for a maximal 

 yield of glyoxylic acid. 



IV. Remarks on the Colour Reaction : Spectroscopic Phenomena. 



Adamkiewicz* observed that the colour produced in the reaction 

 varies from red to violet, the blue element increasing with increase in 

 the amount of acetic acid employed. When glyoxylic acid in aqueous 

 solution is used, unless the solution be very dilute, the colour partakes 

 more of a blue shade than is usually seen with ordinary specimens of 

 acetic acid. But after concentrating the reactive substance of the 

 latter by fractional distillation (supra) or upon large dilution of the 



* Loc. cit., p. 158. 



