G. Edgar — Estimation of Iron and Vanadium. 81 



In the experiments in Table I three standard solutions were 

 used, viz. : — 



1. A solution of potassium vanadate, slightly acidified with 

 sulphuric acid, and containing 11*36 grams of vanadic acid to 

 the liter. This solution was standardized by the method of 

 Holverscheit.* 



2. A solution of ferric alum, slightly acid, with sulphuric 

 acid and containing 14/37 grams of ferric oxide to the liter. This 

 solution was standardized by the very accurate method of 

 JSTewton. f 



3. An approximately tenth normal solution of potassium per- 

 manganate (3*16 grm. per lit.), standardized against a N/10 

 solution of arsenious oxide. 



The details of manipulation were as follows : — Measured 

 portions of the ferric sulphate solution were mixed with por- 

 tions of the solution of vanadic acid, and a current of sulphur 

 dioxide was passed through the slightly acid mixture until the 

 color had changed from red into green and finally into a clear 

 blue. A few centimeters of dilute sulphuric acid were then 

 added, and the solution heated to boiling, the current of sul- 

 phur dioxide being replaced by one of air-free carbon dioxide. 

 When the last traces of sulphur dioxide had been removed, the 

 flask was cooled in running water, the atmosphere of carbon 

 dioxide being maintained, and when thoroughly cool, titrated 

 with potassium permanganate until the color had changed from 

 blue into yellowish green. The solution was then heated to 



Ferric 



















Alum 



I 



II 















in 



KMn0 4 



KMn0 4 















deceive 



r N/10 



x9545 



v 2 o 5 



V 2 5 



Error on 



Fe 2 3 



Fe 2 3 



Error 



lOg 



/ ^ 



"- N 



taken 



found 



V 2 5 



taken 



found 



Fe 2 3 



cm 3 . 



cm 3 . 



grm. 



grm. 



grm. 



grm. 



grm. 



grm. 



35 



31-90 



58-02 



0-1136 



0-1137 



+ 0-0001 



0-1437 



0-1436 



—o-oooi 



35 



31-90 



58-04 



0-1136 



0-1138 



+ 0-0002 



1437 



0-1435 



— 0-0002 



35 



31-85 



58'00 



0-1136 



0-1138 



+ -0002 



0-1437 



0-1433 



— 0-0004 



35 



31-90 



58-00 



0-1136 



0-1136 



±0-0000. 



0-1437 



0-1437 



±0-0000 



20 



25-30 



38-35 



0-0568 



0-0568 



±0-0000 



0-1437 



0-1423 



— 0-0004 



20 



25-29 



38-30 



0-0568 



0-0566 



— 0-0002 



0-1437 



0-1433 



— 0-0004 



20 



15-98 



29-02 



0-0568 



0-0568 



±0-0000 



0-0719 



0-0721 



+ 0-0002 



50 



3850 



77-60 



0-1704 



0-1702 



— 0-0002 



0-1437 



01442 



+ 0-0005 



50 



38-45 



77'60 



0-1704 



0-1704 



±0 0000 



0-1437 



0-1438 



+ 0-0001 



50 



38-45 



77-58 



0-1704 



0-1703 



— o-oooi 



0-1437 



0-1439 



+ 0-0002 



35 



22-50 



48-60 



0-1136 



0-1136 



±0-0000 



0-0719 



0-0720 



+ 0-0001 



35 



22-50 



48*60 



1136 



0-1136 



±0-0000 



0-0719 



0-0720 



+ 0-0001 



35 



22-45 



48-58 



0-1136 



0-1137 



+ 0-0001 



0-0719 



0-Q716 



— 0-0003 



20 



15-97 



29-07 



0-0568 



0-0570 



+ 0-0002 



0-0719 



0-0718 



—o-oooi 



* 



Inaug. Diss., Berlin, 1890. 





f This Journal, xxv, 343. 







Am. Jox 



JR. SCI.- 



-Fourth 



Series, Vol. XXVI, No. 151.— July, 1908. 





