The pH of urea solutions

It has been confirmed that urea increases the measured pH of aqueous solutions. Conductance measurements on acetic acid and colorimetric measurements on p-nitrophenol show that urea increases the dissociation of weak acids. From conductance and pH measurements on ammonium hydroxide-ammonium chloride in urea solution, it is concluded that urea increases the ionization of water. The same conclusion is reached from pH measurements on potassium hydroxide in urea solutions. It is postulated that urea at high concentrations drastically reduces the activity of hydrogen ions, leaving the activities of the other ions more or less unchanged.