The substoichiometric determination of chromium in aluminium alloys

Principles and Applications of Substoichiometric Techniques of Analysis

“…In the latter case, the chelate is usually separated with a cation exchanger. In experiments on the substoichiometric separation of molybdenum with 8-hydroxyquinoline in chloroform we found 23 the reproducibility of the count-rate to be ± 0.3% from 2.0 x 10~3 M solutions in the volume range 3 to 8 ml, while in the extraction of the ion-association compound of chromium(VI) with tetraphenylarsonium chloride 18 the reproducibility was ± 1.3% from 1.0 x 10" 2 M solutions in the volume range 1 to 25 ml. The standard deviation in the first case was 0.6% and in the second case 1.0% It has been pointed out by workers active in the field of substoichiometric analysis 20 ' 24 that a modification of the method can be applied even in cases where the amount of the element isolated by substoichiometric extraction is not strictly independent of the amount of it in solution.…”

“…nT + + Z n " = [ T n Z ] o r g (18) where T + is the heavy cation and Z n~ is the anion to be extracted. The extraction constant is given by -ext…”

“…18 The method was based on the substoichiometric extraction with 1,2-dichloroethane of the ion-association compound of chromium(VI) and tetraphenylarsonium chloride. Most of the common metal ions did not interfere.…”