Mr Fenton, Oxidation in Presence of Iron. 371 



and a little caustic alkali a beautiful but transient violet colour. 

 Ferric chloride gives a deep red colour, and cupric acetate an 

 olive-green precipitate. 



This compound is identical in every respect with the 'secondary' 

 dioximido-propionic acid CH (NOH) . C (NOH) . COOH which 

 Soderbaum obtained from dibromopyruvic acid. 



Oxidation with cupric hydroxide. 



The oxidation -product mentioned above when further oxidized 

 with cupric hydroxide, in presence of alkalies, gives a large yield 

 of mesoxalic acid. 



Taking this result together with those above described con- 

 clusive evidence is afforded as to the constitution of the product — 

 that it is the semi-aldehyde of mesoxalic acid. 



The formation of this substance from tartaric acid under the 

 conditions mentioned might be explained in several ways. At 

 first it was thought probable that dioxytartaric acid was the 

 initial product, and that this gave rise to mesoxalic semi-aldehyde 

 with loss of carbon dioxide and water. But all attempts to 

 prepare the substance from pure dioxytartaric acid, by heat, 

 action of acids or of iron salts, were unsuccessful or unsatisfactory. 

 It was observed however that the product of the action of chlorine 

 on tartaric acid in presence of iron gives, in the first instance, 

 a notable reaction of dioxymaleic acid with iron salts, and it 

 seemed probable that the latter acid might be the initial product 

 in formation of the semi-aldehyde. Starting upon this assumption 

 attempts were made to prepare the semi-aldehyde directly from 

 pure dioxymaleic acid, and these eventually were completely 

 successful. 



When a solution of dioxymaleic acid is treated with a ferric 

 salt, such as ferric sulphate, it is almost quantitatively converted 

 into mesoxalic semi-aldehyde and carbon dioxide, 



C 4 H 4 6 + Fe 2 (S0 4 ) 3 = C 3 H 2 4 + 2FeS0 4 + H 2 S0 4 + C0 2 . 



After removal of the iron salt and free numeral acid the 

 aldehyde remains as a thick syrup. It has not yet been induced 

 to crystallize but experiments are being made in this direction. 



The typical oxidation-products of glycerol which are theoreti- 

 cally possible are eleven in number, namely — glyceric, hydroxy- 

 pyruvic, tartronic and mesoxalic acids, glyceraldehyde, dihy- 

 droxy-acetone, tartronic semi- and di-aldehydes, hydroxy-pyruvic 

 aldehyde, and mesoxalic semi- and di-aldehydes. Of these the 

 first six are well known ; mesoxalic di-aldehyde is known only in 

 form of oxim, and the remaining four were hitherto unknown. 

 The isolation of the semi-aldehyde of mesoxalic acid therefore 

 brings the series one stage nearer completion. 



VOL. XI. PT. V. 27 



