[archibald-fulton] 



ESTIMATION OF IRON 

 Table IV 



249 



The substitution of sulphuric acid for hydrochloric has apparently 

 not rendered the precipitation any more complete. The increase in 

 the amount of iron dissolved as the volume of wash water increases is 

 worth noting. 



It was now considered that sufficient data were available to enable 

 one to correct the values for the iron obtained in its separation from 

 manganese. The correction for the iron remaining in the mother 

 liquor will of course vary with the volume of thé solution from which 

 precipitation took place. For a precipitation carried out under the 

 usual conditions, i.e. for a volume of 100 cc. of solution, to which has 

 been added 20 cc. of concentrated hydrochloric acid, this correction 

 corresponds to 0-0030 gram of ferric oxide. In the case of the wash 

 water the correction amounts to 0-0004 g. of ferric oxide, 75 cc. of 

 washing solution being used, having an acid concentration correspond- 

 ing to 5 cc. of cone, hydrochloric acid in 100 cc. of water. A series of 

 separations were accordingly carried out with mixtures containing 

 25 cc. of iron solution (11-154 grams Fe CI3 per litre) and 50 cc. of 

 manganese solution (22-304 grams Mn CI2 per litre). To these 

 mixtures were added 20 cc. of cone, hydrochloric acid and enough 

 water to give the volumes shown in the table. 



Sec. Ill, Sig. 17 



