464 Gooeh and Peters— Titration of Oxalic A eid. 



be taken up. In the accompanying table are recorded the 

 effects of varying amounts of manganous salt^ in presence of 

 different amounts of sulphuric acid in the reaction of perman- 

 ganate upon oxalic acid. 







Temperature at 



beginning about <. 



?#° a 





Volume 



H 2 S0 4 



Ammonium 





Variation 



at beginning. 



1: I. 



oxalate. 



MnS0 4 .5H 2 0. 



KMn0 4 . 



from 



cm 3 . 



cm 3 . 



JqW cm 3 . 



grams. 



cm 3 . 



standard. 





"130 



5 



25 







23-75 



o-oo 





130 



5 



25 



0-0008 



23*75 



o-oo 





130 



5 



25 



0*0032 



23-75 



o-oo 





130 



5 



25 



0-0160 



23-75 



0^00 



<{ 130 



5 



25 



1- 



23-70 



— 0-05 





130 



5 



25 



2' 



23-75 



o-oo 





130 



5 



25 



2-5 



23-60 



— 0-15 





130 



5 



25 



3-0 



23-40 



— 0-25 





130 



5 



25 



4-0 



23-60 



— 0-15 





f500 . 



5 



25 







23-80 



+ 0-05 





500 



5 



25 



0-0008 



23-80 



+ 0-05 





500 



5 



25 



0-0032 



23-80 



+ 0-05 



<j 500 



5 



25 



1- 



23-70 



-0-05 





500 



5 



25 



2* 



23-40 



— 0-35 





500 



5 



25 



3- 



23-50 



— 0-25 





500 



5 



25 



4- 



23*30 



— 0-45 



ri30 



f io 



25 



1- 



23-80 



+ 0-05 





130 



o o 



Y 



25 



2- 



23-75 



o-oo 





130 



25 



3- 



23-65 



—o-io 





130 



lio 



25 



4- 



23-50 



-0-25 





130 



( 15 



25 



2- 



23-75 



o-oo 



] 130 



15 



25 



4- 



23-70 



— 0-05 





130 



I 15 



25 



5- 



23-50 



— 0-25 





130 



f 30 



25 



2- 



23-75 



o-oo 





130 



•] 30 



25 



4- 



23-70 



— 005 





1 130 



( 30 



25 



5- 



23-75 



o-oo 



From the results given it is evident that the persistence of the 

 Guyard reaction is liable to interfere with the end reaction of 

 oxidation of oxalic acid unless an adjustment is made between 

 the quantity of the manganous salt, the amount of acid, and 

 the dilution. In hot solutions of a total volume of 130 cm3 at 

 the beginning, no more than c 2 grams of the manganous sul- 

 phate should accompany 5 to 10 cm3 of the 1 :1 sulphuric acid; 

 when the total volume at the beginning reaches 500 cm3 , no more 

 than a single gram of the salt should be present with 5 cm3 of the 

 1 : 1 sulphuric acid. The amount of manganous salt may, 

 however, be increased considerably if the quantity of acid is 

 increased. 



