The Oxidation of Cmie Siujar. 225 



required to produce a pink coloration in 5ccs. 



N 

 but as Sees, yq [Fe] is equivalent to (will 



N 

 comliine with) Ice. y^KMn04. 



14-4ccs. of the filtered solution contained as 



N 

 much KMnO^ as lOccs. , KMnO^. 



,•. lOOccs. contained -— — ccs., KMnO- 



14-4 100 



N 

 = 69-44ccs. jQ-^KMnO,. 



and 100-69-44 (i.e., 30-56) y^-milligram 



molecules of KMnO^ have been reduced to 

 MnO.. 

 (ii.) By complete filtration of all solution and separa- 

 tion of all MnOo. 

 The filtrate and washings were then made up to 

 lOOccs. and their value estimated as in (2) (i.), 

 or the whole may be neutralised with excess 

 of ferrous solution as in (1). 

 The precipitated MnO, can also be estimated by (1). 

 The objection to (i.) is that the volume of the 

 precipitated MnO. is not allowed for, and 

 adsorbtion may also exercise an effect on the 

 result. Probably both sources of error are 

 negligible, especially as they tend to neutralize 

 one another. 

 The disadvantage of (ii.) is that it involves the 

 complete filtration of the whole of the solution 

 and thorough washing of the precipitate; 

 operations which occasionally (when the 

 asbestos filter becomes clogged) may be very 

 tedious. 



3. Estimation of the /ofa/ loss of ''active oxygen'' in the 

 liquid. 



