The Oxidation of Cane Sugar. 217 



The K2O was evidently, partly at all events, in combination 

 with the MnaOg, foi' it is difficult to understand how so much 

 alkali could have remained merely adsorbed after the long 

 continued washing to which it had been subjected. 



Preliminary Experiments atid Theory of Action. 



Test tube experiments shewed that sugar solutions stronger 

 than about ten per cent, readily acted on approximately saturated 

 solutions (6'25 per cent.) of potassium permanganate, either on 

 leaving to stand for a short time or immediately on heating to 

 about 30°0. ; in both cases the whole mixture gelatinized, 

 evidently in consequence of the precipitation of a hydrated oxide 

 of manganese. With weaker solutions a higher temperature was 

 required, and the reaction was slower and less energetic, no 

 gelatinization taking place though a precipitate was still formed. 

 The presence of acids such as acetic, hydrochloric and sulphuric, 

 considerably accelerated the action. 



With the object of determining the oxidation products of the 

 sugar, I took solutions of about four per cent, strength, and 

 mixed them in the ratio of one molecule of sugar to 4 molecules 

 of KMnO^ approximately. After boiling and filtering from the 

 precipitated oxide, the solution was neutral to litmus, and 

 effervesced with dilute acids, and gave a white precipitate with 

 silver nitrate, soluble in acetic and other dilute acids, and which 

 blackened on heating. No precipitate was obtained with calcium 

 chloride in presence of dilute acetic acid. 



These tests indicated the presence of carbonates and formates, 

 and shewed the absence of oxalates. 



Possibilities open for the Reaction according to Chemical Theory : 



A. Oxidation of the Sugar. 



(i.) Complete Oxidation : — -to carbonic acid and water, 

 each sugar molecule requiring 24 atoms of 

 Oxygen. Ci^H^^On -^240 = \ 200., + 1 1 H,0. 



(ii.) Partial Oxidation: — to oxalic acid and water, 

 each sugar molecule requiring 18 atoms of 

 oxygen. Ci^H^^On + 18O = GH^C^O^ + SH^O. 



(iii.) Partial Oxidation :— to formic acid., each sugar 

 molecule requiring 12 atoms of oxygen. 

 C12H2A1 + HoO + 72O = 1 2CH A- 



