Thermodynamic constants ofN-(2-hydroxyethyl)piperazine-N′-3-propanesulfonic acid (HEPPS) and (3-[N-morpholinol])-2-hydroxypropanesulfonic acid (MOPSO) from the temperatures 278.15 K to 328.15 K

✍ Scribed by Rabindra N. Roy; Catherine P. Moore; Pamala Lord; Dawn Mrad; Lakshmi N. Roy; William S. Good; Jodi Niederschmidt; Kathleen M. Kuhler

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 132 KB
• Volume: 29
• Category: Article
• ISSN: 0021-9614
• DOI: 10.1006/jcht.1997.0251

✦ Synopsis

Pt N H g, p s 101.325 kPa N buffer m , Na salt of buffer m , NaCl m N AgCl N Ag, 2 1 2 3 where m denotes molality. Values of the second thermodynamic dissociation constant p K 2 Ž . Ž . Žw for N-2-hydroxyethyl piperazine-N Ј-3-propanesulfonic acid HEPPS and 3-Nx. Ž . morpholinol -2-hydroxypropanesulfonic acid MOPSO have been determined from T s 278.15 K to T s 328.15 K. These zwitterionic compounds are useful as secondary standard buffers in the pH range 7.6 to 8.2 for HEPPS, and 7.2 to 6.4 for MOPSO. The p K values for 2 the ionization of HEPPS in the experimental temperature range are expressed by the . . Ž . Ž . equation: p K s 359.23 KrT q 21.0324 y 2.50647 ln TrK ; while, for MOPSO, p K s 2 2 . . Ž . Ž . 432.25 KrT q 22.99923 y 3.08415 ln TrK . The values of the thermodynamic quantities are compared with those for structurally related compounds.