218 Proceedings of the Royal Society of Victoria. 



B. Reduction op the Potassium Permanganate to supply 

 the oxygen necessary for the oxidation of the sugar may also be 

 to one of several conditions. 



(i.) Manganese peroxide : — MnOj. 

 (ii.) Mangattic oxide : — Mn-^O.^. 

 (iii.) Manganoiis oxide : — MnO (in form of a mangau- 



ous salt if in presence of acid), 

 (iv.) A variable mixture of MnOj, Mn^Og and MnO. 



The amounts of oxygen liberated in cases (i.), (ii.) and (iii.), 

 from two molecules of KMn04 is shewn thus : — 

 (i.) 2KMn04 = 2MnO, + K20+jO. 

 (ii. ) 2KMn04 = Mn A + K.p + 4O. 

 (iii.) 2KMn04=2MnO + K20+jO. 



In the case of the sugar being all completely oxidised to 

 carbonic acid, as seems probable, and supposing the KMnO^ to be 

 all reduced to one only of these three conditions, then the 

 number of molecules of KMnO^ required for the oxidation of 

 each sugar molecule will be : — 



(1) 16 :— if MnO, be formed. 



(2) 12 :— if MnA be formed. 



(3) 9-6 :— if MnO be formed. 



In the possible case of formates or oxalates being produced in 

 the reaction, one half or three quarters of these amounts of 

 KMn04 would be required. 



. / N 

 Prehminajj experiments with dilute solutions I ^^^ Sugar and 



— KMnO^j shewed that up to 16 equivalents (molecules) of 



KMn04, may be decolorised for each equivalent of sugar in 

 presence of dilute sulphuric acid. 



In these cases most, if not all of the sugar must have been 

 oxidised to CO., and H.jO, and most, if not all of the KMnO, 

 must have been reduced only to MnO,. 



The action may be tentatively represented as taking place 

 according to this equation if in neutral solution : — 



Ci,H,,On + 1 6 KMnO^ = 8K,0 + 1 6MnO, + 1 200, + 1 1 H,0. 



We must bear in mind, however, that the K,0 is probably in 

 combination with both the MnO, (Smolka, loc. cit., and Morawski 



