224 Proceedings of the Royal Society of Victoria. 



The temperature was more exactly regulated by a vapour 

 pressure thermostat and the effect of air currents minimised by 

 the use of separate covers fitting over the neck of each flask. 



The circulation of the water takes place in a uniform manner, 

 the current passing up through the central cylinder from directly 

 over the flame, and it then spreads out across the shelf and 

 ai'ound the flasks and thermostat, and finally down the sides 

 through openings for that purpose. 



The result is that a thermometer with the bulb placed in any 

 part of the vessel shews readings not differing by more than 1°C., 

 and if kept in the region of the flasks, this difference practi- 

 cally vanishes. 



Where 100°C. was the temperature desired, the flask was 

 simply placed on a sand bath, so heated that the liquid was just 

 kept in a state of quiet ebullition. 



(c) Calculation of Results. 



In the titration of the amount of reduction undergone by the 

 KMnO^ in any experiment, one or more of three methods was 

 employed. 



- 1. Estimation of the amount of MnO.^, precipitated by complete 



filtration of the solution through asbestos, and washing of the 



precipitate until no pink colour of KMn04 remained. 



This precipitate was then at once dissolved in excess of 



N N 



— , or -- [Fe] and then the excess determined by 



10 50 '- -■ ^ 



N 

 titration with — KMnO.. 

 50 



2. Estimation of the KAfnOi reduced to MnO. ; this was 

 done in either of two ways. 



(i.) The liquid and precipitate was made up to lOOccs., 

 and then part of it filtered into a burette and 

 titrated against a fixed volume of [Fe]. 

 A simple calculation gives the amount of KMnOi 

 reduced to MnOo, and this method was 

 employed yi the majority of my earlier 

 experiments. 

 Thus in experiment 2 of Table II., it was found 

 that 14-4ccs. of the filtered solution were 



