[archibald-fulton] estimation OF IRON 251 



solution of ferrous sulphate, according to the regular bismuthate 

 method, or by oxidizing the manganese with lead peroxide in a nitric 

 acid solution, and comparing the color developed with that obtained 

 from a steel of known manganese content. 



In regard to these results it is apparent that the amount of the 

 manganese brought down with the precipitate varies with the con- 

 centration of the hydrochloric acid, the more dilute the acid the 

 greater the weight of the manganese found in the precipitate. The 

 best results will be obtained using the smaller volumes of solution, as 

 both the manganese carried down will be lower and the iron remaining 

 in the filtrate will be a minimum. 



It should be pointed out that the precipitates obtained as set 

 forth in Table I must have contained some manganese. The better 

 agreement here between the amount of iron oxide taken and found 

 must be largely due to this. 



The following final values were obtained from solutions to which 

 had been added 15 cc. of cone, hydrochloric acid and 5 grams of am- 

 monium chloride. It was thought that this concentration of acid 

 might be sufficient to keep the manganese in solution in the presence 

 of this amount of ammonium chloride. The volume of solution from 

 which precipitation took place was in each case 100 cc, prepared by 

 mixing 25 cc. of iron solution containing 11-154 grams of Fe CI3 per 

 litre, 50 cc. of manganese solution containing 22-304 grams of Mn CI2 

 per litre, 15 cc. of concentrated hydrochloric acid and 5 grams of 

 ammonium chloride. The resulting volume was made up to 100 cc, 

 cooled to 7°C. and to this was added the cupferron solution containing 

 4 grams of cupferron made up to a 6% solution. The washing liquid 

 was 75 cc. of a hydrochloric acid solution containing 5 cc of cone 

 hydrochloric acid to 100 cc. of water; this being followed with 25 cc. 

 of very dilute ammonium hydroxide. The two results obtained for 

 each experiment are included in the following table to show the char- 

 acter of the agreement. 



