Abstract

A potentiometric method for determination of OH and high basicity in solid chromium salts has been developed. The sample solution for analysis is highly diluted with distilled water and boiled with stirring for 15 mm. For potentiometric titration (glass electrode) of the weak acids HL(H2L) as well as coordinated ligands a standard solution of NaOH, 0.1 eq/L is used. The ligands are evaluated from the second endpoint in the ApH/zX V= f(VNaOH) plot (meqNH meq). The quantity of OH is found from the difference: meqo- =meq3±—2meq. The basicity of the chromium complex in the tanning salt is calculated by the ratio of the quantities of OH and Cr3 (obtained iodometrically). The proposed method is applied to the determination of the basicity of two different salts (50% basicity). The analytical results show good precision and accuracy (S1= 6—7%; relative error 1—4%).