Volumetric Determination of Small Amounts of Iridium

Abstract

A volumetric procedure is described for determining small amo-unts of iridium (from 2 to 20 mgm.). A solution of the metal is heate-d to dense fumes with sulphuric acid, codled, dilr,t"d rvith water, and then oxidized lvith an excess of cerium (IV)'sulphate solution. The resultant solution is titrated rvith a standard 0.01 N iron (Ii) sulphate solution, the course of the titration being followed potentiometrically. in solutions containing other platinum metals it has been iound possible to determine iridium directlf in some cases by this.procedure; in other cases it w'as found necessary to remove osmium as the volatile tetroxide prior to oxidizing with cerium (I\i) sulphate. The method.is probably less accurale than exisLinlg gravimetric prtcedrires. but offer' considerable advanrage in simplicity.

Coulometric and titrimetric reduction of iridium fumed in perchloric acid

“…Analogous iridium trimers with mixed 4,4,3 and 4,3,3 oxidation states have been reported (15,16). This hypothesis is further supported by the absorption spectra (Figure 3), for that of the fumed solution (5,5,4) differs only in intensity from that of the fumed solution reduced at +0.83 V (5,4,4). This behavior is characteristic of Class III-A mixed oxidation state compounds (17).…”

“…Heating with an excess of Ce(IV) after an H2SO4 fuming has also been used with conflicting claims of an Ir(IV) product (4) and a species that could be titrated through the states +4.5 to +3.5 to +3.0 (5).…”

Spectrofluorimetric determination of submicrogram amounts of zirconium with Calcein Blue

“…This may easily be accomplished, however, by modifying the extraction procedure when iron is present so that iron(III) is first extracted as its oxinate before the niobium extraction. In the presence of up to a 100-fold molar excess of iron(III), 5 ml of 4% citric acid should be added to the sample solution and the pH adjusted to 2.0. The solution should then be extracted twice using a 5 % solution of oxine in chloroform.…”