Chromic and Arsenious Acids. 



37 



Cr0 3 taken. 



Cr0 3 found. 



Error. 





grm. 



grm. 



grm. 



1 



1001 



0*1004 



0-0003 + 



2 



0-1005 



0-1004 



o-oooi — 



3 



0-1006 



0-1007 



0-0001 + 



4 



0-1004 



0-1011 



0-0007 + 



5 



0-1009 



01009 



o-oooo 



6 



0-1002 



0-1003 



0-0001 + 



1 



o-ion 



0-1004 



0-0007 



8 



0-1007 



0-1007 



o-oooo 



9 



0-0401 



0-0395 



0-0006 — 



10 



0-0402 



0-0388 



0-0014 — 



11 



0-1001 



0-1018 



0-1017 + 



12 



0-1009 



0-1007 



0-0002 — 



13 



0-1007 



0-1011 



0-0004 + 



14 



0-1005 



0-1017 



0-0012 + 



15 



0-1004 



0-1010 



0-0006 + 



16 



o-iooo 



0-1032 



0-0032 + 



17 



0-1005 



0-1006 



0-0001 + 



Remarks. 

 The iodine acted 20 minutes 



(c u a 



a a ft 



" 2 hours 



u « a 



Rochelle salts used 



- 5 grm. ferric alum present 



I grm. ferric alum present 



Rochelle salts used 



1 grm. ferric alum present. 



In three of the above experiments the process was carried 

 through in the presence of a ferric salt with fairly successful 

 results. The presence of the brown precipitate, however, 

 makes the end reaction rather difficult to determine. If, how- 

 ever, the precipitate be allowed to settle after each addition of 

 iodine, the color can be detected very readily in the supernatant 

 liquid. 



Among volumetric processes of great delicacy this process 

 naturally does not find its place. It is, however, interesting to 

 know to what degree the reaction may be depended upon for 

 analytical purposes. 



