On the protonation of glycocholate and glycodeoxycholate ions

The protonation of glycocholate (GC-) and glycodeoxycholate (GDC-) ions was studied at 25 degrees C and in N(CH3)(4)Cl as an ionic medium at concentra tions 0.100, 0.500 and 0.800 mol L-1 by measuring the electromotive force o f a galvanic cell containing a glass electrode, as a function of acidity of solution. Also the solubility of glycocholic and glycodeoxycholic acids wa s determined in the same experimental conditions. The protonation constants of GC- and GDC- were determined and it was found that a further protonatio n of HGC occurs by increasing acidity. Its protonation constant was also de termined.