“…Titrations for the certification of standards such as K2Cr207 (177), for covering a wide range of concentrations (68), and with three constant-current levels (76) have been described. programmable desk calculator can control the whole system (80). Photometric monitoring has proved useful in automated devices, especially those designed for the determination of C02 or other acidic substances (29,33,40,118,170,171).…”