Calculations of Ph for High-temperature Sulfate Solutions At High Ionic Strengths.
Staples-BR; Holcomb-GR; Cramer-SD
Corrosion 1992 Jan; 48(1):35-41
Corrosion studies at the U.S. Bureau of Mines on stainless steels in acid sulfate solutions prompted the development of procedures to calculate the ph for solutions at temperatures to 300 deg c. This general method for calculating the ph of high-ionic-strength aqueous solutions at elevated temperatures is an alternative to instrumental ph measurement techniques and is illustrated for the h2o-na2so4- h2so4 system. The ph is calculated from the partial dissociation of hso-4, while accounting for the buffering effects of completely dissociated na2so4 and h2so4. Modern values for the temperature- dependent second dissociation constant of h2so4 and the extended debye-huckel limiting law slopes are used in the calculations. Uncritical selection of thermodynamic data can result in differences in calculated ph that exceed 0.5 Ph unit in the temperature range 200 to 300 deg c.
Corrosion, V. 48, No. 1, Jan. 1992, PP. 35-41