The accuracy of pH measurement of boiler water with caustic treatment is badly influenced by temperature.Appropriate STC(Solution Temperature Coefficient)was needed in order to obtain accurate pH measurement when the sample temperature is much beyond 25 ℃(reference temperature).The theoretical derivation process of STC was complicated and the result uncertainty was great.Therefore

an efficient and reliable experimental method to determine the STC was presented

and the setting methods of STC value for common domestic online pH analyzers were introduced.Results showed that the STC of NaOH treated boiler water was between 0.026 pH/℃ and 0.028 pH/℃

which was close to that of weak electrolyte alkaline solution by calculation but quite different from that of pure water

common water and strong electrolyte solution.Proper selection of pH analyzer with STC compensation and setting function is important

and to ensure the accuracy of pH measurement for boiler water

the STC value should be rightly set.