Evaluation of the gravimetric tetraphenylarsonium method for the determination of Tc(VII).
Solubility losses in the gravimetric tetraphenylarsonium method for determining pertechnetate have been evaluated. Liquid scintillation counting was used to measure the beta(-) activity of (99)Tc in the filtrate, and indicated solubility losses of about 1% in analyses yielding 40-50 mg of precipitate. The solubility product Of (C(6)H(5))(4)AsTcO(4) is estimated to be (8.6 +/- 0.2) x 10(-10) at room temperature (24-25 degrees ) and K(sp) for (C(6)H(5))(4)AsReO(4) at approximately 21-23 degrees is estimated at (2.6 +/- 0.3) x 10(-9). Both values are satisfactory for gravimetric purposes, but to keep solubility losses within 1% at least 40mg of (C(6)H(5))(4)AsTcO(4) or 80 mg of (C(6)H(5))(4)AsReO(4) should be obtained (assuming 20 ml of solution, 20-30% excess of precipitant and 6 or 7 washes with 5-ml portions of distilled water).
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Department of Chemistry, Indiana University-Purdue University, Fort Wayne Campus, Fort Wayne, Indiana 46805, U.S.A.