226 Proceedings of tJte Royal Society of Victoria. 



(i.) This may be calculated from 1 and 2 (ii. combined). 

 The concordance of the results so obtained is 

 a useful check on the accuracy of the work. 



(ii.) It may also be determined directly by adding 



excess of ferrous solution directly to the 



liquid and then titrating back with standard 



KMnO^ in the usual way. 



This method is superior to the others, both in 



point of accuracy and of speed T/hen only a 



small amount of MnO„ has been precipitated, 



N 

 for then 50ccs. of j^S [-^^-J (equivalent to 



N 

 the 50ccs. of ^KMnO^ originally present) 



can be directly added, the same pipette being 



used for the measurement of both solutions, 



and the excess of ferrous salt readily deter- 



N 

 mined by titration with ^KMnO^. 



(d) Explanation of tables of results. 



The columns indicating the time and temperature of experi- 



N N 



ments and the amounts of p-^^'^-^^^04> ^^-ftr sugar and the amounts 



N 



-nH2S04 do not need further elucidation. 



The results of the titrations have been given in one of three 

 columns according to the method of estimation. 



a. The amount of KMnO^ reduced to MnO.. expressed in 

 jiy milligram molecules. It will be noted that 

 originally 1 milligram molecule of KMnO^ was 

 present. 



/3. The amount of MnO„ precipitated, expressed in yi^j 

 milligram molecules. 



y. The loss of '■'■active oxygen^^ in y^^ milligram atoms. 



Originally 2-5 milligram atoms of active oxygen were 



present. 



Another column has been added, giving the number of oxygen 



atoms abstracted from the solution /ifr molecule of sugar employed. 



