H. D. Newton — Iron by Potassium Permanganate. 345 



an appreciable amount of hydrochloric acid present in solution. 

 Therefore it is advisable if the original solution is made with 

 hydrochloric acid, to evaporate to dryness and convert the 

 chloride to sulphate by use of concentrated sulphuric acid. 

 Upon addition of the sulphuric acid a white pasty mass of 

 basic ferric sulphate is formed which rapidly goes into solution 

 on diluting with water and warming. As titanous sulphate 

 prepared in the above manner always contains some iron, it is 

 necessary to make a correction for this, by treating with bis- 

 muth oxide an amount of the solution equal to that used, filter- 

 ing and running in potassium permanganate to color. This 

 correction should not amount to more than 0"l cm3 when work- 

 ing with - 3 grm. of ferric oxide. 



If these simple precautions be taken, ferric iron may be 

 determined with rapidity and exactness by reduction with 

 titanous sulphate, and subsequent titration with potassium 

 permanganate. 



