368 Peters and Moody — Determination of Per sulphates. 



Method of LeBlanc and JEckardt. 



The reagents used in our experiments were a solution of 

 ammonium persulphate, 10 grm. of the salt to the liter ; an 

 acidified solution of ammonio-ferrous sulphate, 20 grm. to the 

 liter ; an approximately tenth-normal solution of potassium 

 permanganate ; and sulphuric acid of half strength. The 

 standard of the potassium permanganate solution was deter- 

 mined by comparison with a solution of arsenious oxide.* 

 The effect upon the reaction of variations in time, temperature, 

 and amount of ferrous salt were tried, and the results given in 

 Table I. 







Table I. 







Yolume 



of liquid 100 cm3 . 



Ammonium 

 persulphate, 



10 grm. 



to liter. 

 cm 3 . 



(NH 4 ) 2 Fe(S0 4 ) 2 -6H 2 

 solution 

 20 grm. to liter. 

 cm 3 . 



KMn0 4 

 app. N/10, 



to oxidize 

 the excess of 



ferrous salt. 

 cm 3 . 



(NH 4 ) 2 S 2 8 

 , calculated 

 from ferrous 

 salt oxidized. 

 Treatment. grm. 







A 



Heated 10 min. 



12-5 



25 



2-11 



60°-80° 0-1216 



125 



25 



2*18 



" 0-1209 



12-5 



25 



2*11 



" 0-1216 



125 



25 



2-11 



" 0-1216 



12-5 



50 



15-00 



" 0-1218 



25-0 



50 



4-21 



" 0-2426 







B 



Stood 11 hours. 



12-5 



26 



1-89 



21°-25° 0-1214 



12-5 



26 



1-80 



" 0-1224 



12 5 



40 



8-75 



" 01221 



12-5 



40 



8-75 



" 0*1221 



12-5 

 12-5 



Carbon dioxide above the liquid. 



Stood 11 hours. 

 40 8-75 21°-25° 0*1221 



40 8-78 " 0-1218 



In section A are given the results of experiments obtained 

 by heating the mixture of persulphate, ammonio-ferrous sul- 

 phate, sulphuric acid, and water, on the steam bath for ten 

 minutes, at a temperature of 60°-80°. In section B are 

 recorded the results of experiments in which the same mixture 

 was allowed to stand 11 hours at the ordinary room tempera- 



* Gooch and Peters, this Journal, viii, 125. 



