Can any one tell me the pH values at which three different hydroxyl groups attached to triethanolamine may get protonated?

I have noted that if a solution containing 0.1 M triethanolamine adjusted to pH 5.3 is mixed with soils of pH 4.5 or 6.5, the suspension pH is maintained near to 5.3 +_ 0.2. 

16 May 2017 1,340 2 View