Deuterium Isotope Effects on the Second Ionization Constant of Aqueous Sulfuric Acid from 25 °C to 200 °C using Raman Spectroscopy

Second ionization constant of sulfuric acid in H2O and D2O from 150 to 300 °C at p = 11.5 MPa using flow AC conductivity

“…The two previous high temperature studies 5,22 of the second ionization constant of sulfuric acid in heavy water are in disagreement above 100 1C: Yacyshyn et al 22 observed DpK 2a,m E 0.425 AE 0.076 at all temperatures while Lietzke and Stoughton 5 saw the DpK 2a,m decrease with temperature to zero isotope effect at 200 1C, and a negative isotope effect at 225 1C. Yacyshyn et al 22 explained this discrepancy by suggesting that glass dissolution interfered with the measurements by Lietzke and Stoughton 5 at high temperatures. For this reason, the 25 1C DpK 2a,m values from Drucker, 26 Lietzke and Stoughton, 5 and Yacyshyn et al 22 were fitted using eqn (41) with the high temperature data from only Yacyshyn et al 22 and this work.…”

“…61 For consistency with other studies, the pK 2a,H,m = Àlog K 2a,H,m . After critical examination of the existing data for the ionization of bisulfate, [14][15][16][17][18][19][20][21][22][23][24][25] only the studies by Quist and coworkers, 16,17 Hnedkovsky et al, 23,24 Rudolph, 21 and Yacyshyn et al 22 were included in the equation of state fit for the pK a,H,m . The original work by Noyes 25 was not included because the data analysis is poor compared to modern theories of electrolyte solutions.…”

“…Several authors [14][15][16][17][18][19][20][21][22][23][24][25] have used specialized techniques to measure the second dissociation constant of sulfuric acid at elevated temperatures in light water, however, discrepancies exist among the data. Conductivity methods were used in the pioneering work by Noyes, 25 and in later studies by Ryzhenko, 14 Quist and coworkers, 16,17 and Hnedkovsky et al 23,24 Solubility studies were performed by Lietzke et al 15 on Ag 2 SO 4 to 225 1C, and by Marshall and Jones 18 using CaSO 4 to 350 1C.…”

“…Oscarson et al 19 used a flow calorimetric procedure and Dickson et al 20 used potentiometric titrations in aqueous sodium chloride media. Most recently, Rudolph 21 and Yacyshyn et al 22 used Raman spectroscopy with quartz cells to measure the bisulfate ionization constant. The first study to report a heavy water equilibrium constant for the second ionization of sulfuric acid was by Drucker 26 who used electrochemical methods at room temperature.…”

“…Lietzke and Stoughton 5 used the solubility of Ag 2 SO 4 in D 2 O to determine the pK 2a,D,m to 225 1C, and Yacyshyn et al 22 measured the pK 2a,D,m to 200 1C using Raman spectroscopy, where the subscript 'm' indicates the hypothetical 1 mol kg À1 standard state. The two high temperature studies show contrasting results: one study measures a constant isotope effect 22 and the other measures an isotope effect that decreases with increasing temperature. 5 This work used a state-of-the-art flow AC conductivity instrument to measure the second ionization constant of sulfuric acid in light and heavy waters from 150 1C to 300 1C at p = 11.5 MPa.…”