THE OXIDATION OF CANE SUGAR BY 



NITRIC ACID 



By F. D. CHATTAWAY, F.R.S. 



For over a hundred and fifty years the action which takes 

 place when cane sugar is oxidised by nitric acid has attracted 

 the attention of chemists and its spectacular character, from 

 the torrents of nitrogen peroxide evolved, still makes it a 

 favourite laboratory experiment. It has considerable his- 

 torical interest, for it was from the product of this action that 

 Bergman about 1776 first isolated oxalic acid. 



From the testimony of several of his friends it appears 

 that Scheele had identified the acid shortly before, though 

 whether he obtained it from sugar or from wood-sorrel is not 

 clear, for he never published any account of his work. 



Thomson, in his famous History of Chemistry, writes : " That 

 Scheele has nowhere laid claim to a discovery of so much 

 importance as that of oxalic acid, and that he allowed Berg- 

 man peaceably to bear away the whole credit, constitutes one 

 of the most remarkable facts in the history of chemistry." 



It is, however, to Bergman that we owe the first published 

 account of the properties of oxalic acid and of its production 

 from sugar. He regarded the acid as contained in the sugar 

 and as being liberated from it by the action of the nitric acid, 

 for he thus begins his treatise : 



" Sugar being justly considered as an essential salt, it 

 will readily be granted that it contains an acid. This acid 

 may be separated and exhibited in a crystalline form by the 

 following process." He then describes the action of nitric 

 acid upon it as follows : 



Let one ounce of the finest sugar in powder be mixed 

 in a tubulated retort with three ounces of strong nitric acid 

 whose specific gravity is nearly 1-1567. When the solution 

 is completed and the most phlogisticated part of the nitric 

 acid has flown off, let a receiver be luted on and the solution 

 gently boiled ; in this process an immense quantity of nitrous 

 air is somewhat violently discharged. When the hquor 

 acquires a dark brown colour let three ounces more of nitric 

 acid be poured on and the boiling continued until the coloured 

 and smoking acid has entirel}^ disappeared. Let the liquor 



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