Table 1.

pK_a Values for Acids in 100% Water (Low Ionic Strength)

acid	25 °C	37 °C
nicotine	pKa,1 = 3.10,a pKa,2 = 8.01a	pKa,1 = 2.77,b pKa,2 = 7.65b
benzoic	pKa = 4.20c	pKa = 4.20c
vanillin	pKa = 7.38c	pKa = 7.27c
levulinic	pKa = 4.64d (18 °C)

^aBarlow and Hamilton (1962).¹⁹

^bClayton, Vas et al. (2016).²⁰

^cChristensen and Hansen (1976).²¹

^dKortüm, Vogel, and Andrussow (1961).²²