METHOD OF THE pH-METERS CALIBRATION Russian patent published in 2018 - IPC G01N27/416 

FIELD: electricity; measurement technology.

SUBSTANCE: invention can be used on thermal and nuclear power plants in ultrapure waters such as the power unit condensate and feedwater. In the pH meters calibration method, consisting in the correcting agent dosing – the medium pH changing substance, in particular, ammonia, into the cooled working medium sample stream, with the electrical conductivity and temperature subsequent measurement, the pH value calculation and the calculated pH value installation at the pH meter, using the regular line for measuring the electrical conductivity of the cooled down to the temperature of 25±10 °C of the N-cationized sample of feed, boiler water or the condensate type water, setting the working medium flow rate of 5–10 l/h, measuring the specific conductivity (χ_H²⁵) value, introducing the correcting reagent with molar concentration of 0.001–0.002 into the working medium flow, increasing the medium specific electrical conductivity to not more than 10 mcS/cm, for which setting the correction reagent flow rate to be 0.5–1.0 l/h, at that, as correcting reagent for the alkaline medium using the ammonia aqueous solution, measuring the electric conductivity (χ_K²⁵) in the working medium with aqueous ammonia solution flow and determining the pH value for the alkaline medium with the ammonia dosage according to the proposed expression: pH_K²⁵=8+lg(3.68⋅χ_K²⁵-1.09⋅χ_H²⁵-1.91⋅(χ_H²⁵)²), for weakly acidic medium, using the sodium hydrogen carbonate, sodium chloride and carbonic acid, taken in equal concentrations, mixture solution as the correcting reagent, pH value is determined from the carbonic acid dissociation constant value by the first stage, taking into account the process conditions equal to 6.37 pH units, and for the medium close to neutral, sodium hydrogen carbonate solution is used, which pH²⁵ value is 8.33.

EFFECT: invention provides increase in the calibration results accuracy and reproducibility in the pH working range from 6 to 10 both laboratory and board pH meters, as well as the calibration method simplification.

1 cl, 1 tbl, 1 dwg