Abstract
A determination was made of the average valence of bismuth in the Bi-Sr-Ca-Cu-O superconductor using the o-tolidine spectrophotometric method to lessen the amount of sample required. The chlorine liberated by a reaction between Bi(V) and hydrochloric acid was stoichiometrically equivalent to Bi(V) in the sample. Bi(V) was determined over the range of 0.01-0.10mg based on the absorbance observed with the oxidant of o-tolidine. The total bismuth was determined by spectrophotometry after the extraction of Bi(III) with Zephiramine and iodide ions into chloroform. By a Bi(V) determination with o-tolidine, the amount of consumed sample could be decreased down 0.5mg. Although Cu(III) did not hinder the determination of Bi(V), Pb(IV) did. In the 2212 Bi-Sr-Ca-Cu-O sample having a high Tc of 90K, the average valences of bismuth was confirmed to be from 3.12 to 3.17.
