Accurate measurements of the concentration of hydrogen ions with a glass electrode: calibrations using the Prideaux and other universal buffer solutions and a computer-controlled automatic titrator

Several universal buffer solutions, variably composed of 3-5 mM potassium acetate, potassium dihydrogen phosphate, ethylenediammonium diChloride, and borax, were examined as a convenient and reliable method for calibrating a glass electrode to read true hydrogen ion concentration.From the results of nineteen titrations, 25°C, pH 2 to 12, 1.05 to .20 M (KCl) , pH meter (adjusted with NBS pHS 4.008 and 6.865 buffers) readings, pH , using a Beckman 39501 combination m electrode, can be converted to -log[H+], p[H], by pH =~' + 5' p[H] m 2 where ~' = 0.2269 -1.949I + 7.756 I , o(~') = .019pH and 5' = 0.9657 + .4752I -1.532 1 2 , 0(5') = .0022.At I 0.1 M 2 pH = .110+ .998p[H].A FORTRAN computer program was coded m to calculate ~' and 5' for any titration in the range 0 to 40°C and 0 to 0.3 M (KCl), and for any combination of the four buffer components.A microcomputer-controlled automatic titrator, programmed in BASIC, was used to collect the potentiometric data.