S. E. Moody — Hydrolysis of Salts. 



m 







Table I. 







FeS0 4 . 

 cm 3 . 



25 



K 2 Mn 2 8 . 

 cm 3 



10-60 



Fe. 

 grm. 



0-0734 





Iodine 

 equivalent, 

 grm. grm. 

 (Mean.) 

 0-3326 ] 



25 



10-60 



0-0734 





0-3326 | 





25 



1057 



0-0732 





0-3317 J- 



0-3322 



25 



10-58 



0-0733 





0*3320 





25 



10-59 



0-0734 





0-3323 J 









Table II. 







FeS0 4 . 



EX KI0 3 . 



Time in Na 2 S 2 3 

 minutes. 



Iodine 

 calculated. 



Diff. 



cm 3 . 



grm. cm 3 . 





cm 3 . 



grm. 



grm. 



25 



1-0 15 



30 



26-67 



0-3324 



+ 0-0002 



25 



1-0 15 



30 



26-68 



0-3325 



+ 0-0003 



25 



1-0 15 



30 



26-65 



0-3321 



—o-oooi 



25 



1-0 15 



30 



26-67 



0-3324 



+ 0-0002 



25 



1-0 15 



30 



26-66 



0-3323 



+ 0-0001 



So it appears that the hydrolysis of ferrous sulphate is com- 

 plete in the presence of the iodide-iodate mixture and that the 

 iodine set free is an exact measure of the S0 4 -ion present and 

 of the iron in the ferrous sulphate of ideal composition. 



Chi 



omium. 



Chromium sulphate, in the form of the alum, was next ex- 

 amined. The standard of the solution was found by precipi- 

 tating with ammonia and igniting the chromic hydroxide to 

 constant weight. For the purpose of comparison other por- 

 tions of the solution were treated with the iodide-iodate mix- 

 ture and boiled for half an hour in a trapped Erlenmeyer 

 beaker to expel the iodine. A few drops of sodium thiosul- 

 phate were added to take up the last trace of iodine and thus 

 insure complete hydrolysis. The precipitate was filtered oif 

 on asbestos, washed with boiling water and ignited to constant 

 weight. Results of these experiments are given in the follow- 

 ing table: 



Table III. 



prox. N/10 

 chrome 

 alum. 



Precipitant. 

 Ammonia. Iodide-iodate 

 mixture. 

 Cr 2 3 Cr 2 3 

 found. found. 



Mean of 

 entire series. 



cm 3 



grm. grm. 



grm. 



25 



0-0643 0-0638 "| 





25 



0-0638 0-0645 | 





25 



0-0646 0-0641 )■ 



0-0642 



25 



0-0641 0-0640 J 





25 



0-0644 0-0643 





