AUTOMATED, HIGH-PRECISION COULOMETRIC TITRIMETRY .2. STRONG AND WEAK ACIDS AND BASES

Automated constant-current coulometric acidimetry, based on Faraday's Laws, is uncertain to less than 1 part in 20000 (relative standard dev iation) and requires no chemical standardization. It is applicable to strong and weak acids and bases, with bases back-titrated after additi on of excess strong acid. Initial setup and sample introduction are th e sole manual steps. Assays of HCl, benzoic acid, Na2CO3, and tris(hyd roxymethyl)aminomethane are presented. In the endpoint determination p rocedure, a generalized titration equation yields the theoretical char ge remaining to the endpoint before each charge addition. The ratio of the experimental to the theoretical charge for the preceding aliquot corrects for experimental deviations.