28 



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



great ease if not more than 4 to 5 grammes of phenylhydrazine hydro- 

 chloride have been added to the final distillate obtained after oxidising, 

 as above, 1 litre of acetic acid, nearly neutralising the mixture and 

 distilling. We prepared the compound from formaldehyde, and found 

 it to agree with our product in every particular. 



Formaldehyde certainly does not yield the proteid reaction, and its 

 formation when acetic acid is treated as described seems to be in itself 

 evidence for the formation of giyoxylic acid during the process, as it 

 is difficult to see how it could arise during the oxidation of acetic acid 

 if not from a preliminary formation of giyoxylic acid with subsequent 

 loss of carbon dioxide. 



But its formation adds greatly to the difficulty of obtaining pure 

 the hydrazone of giyoxylic acid itself, especially as the precipitate 

 produced by phenylhydrazine undoubtedly contains, in addition to the 

 compound of Wellington and Tollens, smaller amounts of the deriva- 

 tives described by J. W. Walker/"" 



After the nature of this bye-product was recognised we modified our 

 procedure by neglecting the earlier portions of the final distillate 

 which contains, of course, the greater part of the formaldehyde. 

 Phenylhydrazine hydrochloride added to the latter half, or two-thirds, 

 of such a distillate yields a precipitate which forms more slowly than 

 that obtained when the whole is dealt with. After twenty-four hours 

 it is usually crystalline and of a yellow colour, growing darker with 

 further standing. 



We found it easier to obtain a product with a constant melting 

 point by recrystallising from hot water rather than from an organic 

 solvent, prolonged heating with the water being at any stage avoided. 

 This treatment involves considerable loss, however, and we obtained 

 only about 4 decigrammes of the hydrazone after oxidising 3 litres of 

 acetic acid. This, however, had all the characters of giyoxylic 

 hydrazone, and melted sharply at 137°. 



0*204 gramme gave 30*4 c.c. moist N at 16° and 750 mm. X = 

 17-14 per cent. Calculated for C s H s OoX 2 = 17-07. 



When acetic acid has been oxidised as described and the mixture 

 partially neutralised and distilled, the distillate, when treated with 

 excess of chalk, will yield, after standing and filtering, the reaction for 

 giyoxylic acid described by Perkin and Duppa. If after treatment 

 with chalk a slight excess of calcium hydrate be added, and the mix- 

 ture concentrated in vacuo to about one-third its original bulk, this 

 reaction with aniline oxalate is obtained in a highly characteristic- 

 manner. 



The methods we have hitherto employed do not yield the giyoxylic 

 acid in solutions of sufficient strength to permit of its calcium salt 



* ' Joum. Ohem. Soc./ 1896, vol. 69, p. 1280. 



