Potassium Permanganate and Sulphuric Acid. 303 



phuric acid (always previously diluted with an equal volume of 

 water, and cooled) and, after the lapse of time indicated to 

 add oxalic acid in quantity a little more than sufficient to 

 bleach the entire amount of permanganate, warm to about 80° 

 C, and titrate the residual oxalic acid by gradual addition of 

 more permanganate. The difference between the amount of 

 permanganate needed under the conditions to destroy the 

 known amount of oxalic acid and that used in the determina- 

 tion of the standard should measure the oxygen lost by the 

 permanganate under the action of the sulphuric acid. The 

 results and details of these experiments are given below. 



Table I. 



H 2 S0 4 

 [1:1] 



cm 3 



2 

 4 

 6 

 8 

 10 



Water. 

 cm 3 



K 2 Mn 2 O e 

 in decinormal 

 solution. 

 cm 3 

 A. 

 Treated immediately 



10 

 10 

 10 

 10 

 10 



Percentage of 



H. 2 S0 4 [1 : 1] 



in solution 



during action. 



JO 

 20 

 30 

 40 

 50 



Percentage of 



K 2 Mn 2 8 

 used as com- 

 pared with that 

 required by theory. 

 cm 3 



100 



100 



101-5 



101-6 



101-9 



Treated after standing eight hours at ordinary temperature. 



2 

 4 

 6 

 8 

 10 



2 

 4 

 6 

 8 

 10 



10 

 10 

 10 

 10 

 10 



10 

 20 

 30 

 40 

 50 



99 



99 



101 



105 



il5 



C. 



Treated after standing five days at ordinary temperature. 



10 

 10 

 10 

 10 

 10 



10 

 20 

 30 

 40 

 50 



104 

 121 

 149' 

 155 



156 



D. 



Treated after standing one and one-half hours at 80°-90° 0. 

 2 8 10 10 101 



4 6 10 20 143 



6 4 10 30 135 



8 2 10 40 149 



10 ... 10 50 155' 



It is manifest from an inspection of Table I that the de- 

 composition of the permanganate increases directly in each 

 series of experiments with the increase in the proportion of 



