KINETIC METHOD FOR DETECTING RHODIUM Russian patent published in 1998 - IPC

FIELD: medical engineering. SUBSTANCE: method involves applying sulfarsazene at 4.6-7.5 10^-6 M concentration as periodate reduction agent. The reaction is conducted in background acid medium like 2.0-3.5 M acetic acid solution, 1.0-1.8 M boric acid solution, 2.0-3.5 M phosphoric acid solution at 3.4-3.8 pH of reagent mixture. The background acid medium inhibits catalytic activity of some interference elements concomitant to rhodium and promotes increase in catalytic activity of rhodium. The method involves adding in series 0.7 ml of 8.7 10^-5 M concentration sulfarsazene solution, 1.0 ml of 2.8 M acetic acid solution, 1.0 ml of 1.4 M boric acid solution, 1.0 ml of 2.8 M phosphoric acid solution, 0.5 ml of 0,6 M sodium hydroxide solution to reach 3.6 pH state and 0.5 ml of rhodium solution under study and 2.0 ml of distilled water. The mixture is stirred and 3.5 ml of periodate solution are added at 1.7 10^-2 M concentration. Stopwatch is set simultaneously with periodate solution being added. The reagent mixture is placed into photoelectric colorimeter (λ= 440 nm) cell (l=20 mm) connected to self-recording potentiometer. 1 later after reaction starting, self-recording unit is switched on and kinetic curve is recorded during 2-3 min. Kinetic curve slope angle tangent (tgtgα) being proportional to rhodium contents is determined using graphical method. Rhodium concentration is determined from calibration curve drawn in tgtgα-C(Rh) coordinates. EFFECT: enhanced accuracy in determining trace concentrations of rhodium in production waste. 4 tbl