244 On the Oxidation of Ferrous Salts 



10 c.c. of this solution oxidise o-i gramme iron from ferrous to 

 ferric salt. 



Perchlorate of Potassium. The perchlorate was obtained from 

 the University laboratory, and was very pure. On analysis 

 the following results were obtained: 



\\Yight of salt . . . . . . . . 0-6208 gramme 



uht of salt after heating (KC1) .. 0-3330 



1 'inference oxygen .. .. .. 0-2878 ,, 



Chlorine in residue . . . . . . 0-1581 



\Vlu-nce we have the following composition per cent.. 



Found in Calculated 



salt in KC1O 4 



Potassium . . . . . . 28-18 28-22 



Chlorine . . . . . . 25-46 25-61 



Oxygen .. .. .. 46-36 46-17 



100-00 100-00 



3-0938 grammes KC1O 4 oxidise 10 grammes iron from the 

 ferrous to the ferric state. 3-0940 grammes were dissolved in 

 warm water and made up to a litre at 9 C. 



titrate of Potassium. 6-018 grammes KNO 3 oxidise 10 

 grammes iron from the ferrous to the ferric state. 6-019 

 grammes were dissolved in water and made up to a litre. The 

 nitrate of potassium was purified by recrystallisation. 



The sulphuric acid used to acidify the solutions was made 

 by diluting I part by weight of pure oil of vitriol with 9 parts 

 by weight of water. It contains, therefore', very closely one 

 gram-molecule per litre (H 2 SO 4 ). 



Permanganate of Potassium. This solution was made by dis- 

 solving 3-163 grammes crystallised salt in water and making up 



to a litre. 3-162 grammes = -- = o-O2KMnO 4 . Tested 



with the double sulphate of iron and ammonia, 17-9 c.c. were 

 found to be required to oxidise o-i gramme iron from the 

 ferrous to the ferric state. 3-163 grammes KMnO 4 oxidise 

 5-602 grammes iron from ferrous to ferric, therefore 17-9 c.c. 

 of the above solution ought to oxidise 0-1003 gramme iron. 



It is well known that the use of permanganate of potassium 

 for titrating ferrous salts in hydrochloric acid is discouraged, 

 and indeed prohibited by the highest authorities in analytical 

 chemistry. As a matter of fact, however, there is very little 



