Monograph - Metrohm

Titration of bases6 Titration of basesThe titrations were carried out in the «pH range»** of the titrator in the MET mode(volume increments 0.10 mL, fixed delay period 5 s).** See under 5 «Titration of acids»Electrodes1) 6.0229.100 Solvotrode, electrolyte LiCl sat. in ethanol2) 6.0229.100 Solvotrode, electrolyte TEA-Br c = 0.4 mol/L in ethylene glycol(TEA-Br = tetraethyl ammonium bromide)Bases tested (0.1 mol/L in ethanol)- Ethanolamine; pK B = 4.56- Aniline; pK B = 9.42- Urea; pK B = 13.80Titrantsa) c(HClO 4 ) = 0.1 mol/L in glacial acetic acidb) c(HCl) = 0.2 mol/L in isopropanol (IPA)SolventsEthanol Dioxane/IPA 1:1Acetone MIBK/glacial acetic acid/toluene 1:1:1 (DIN/ISO 3771)Acetonitrile Toluene/IPA/H 2 O 500:495:5 (ASTM D 664)2.50 mL of the tested base was treated with 50 mL of the corresponding solventand titrated with HClO 4 or HCl.ResultsA) Ethanolamine (pK B = 4.56)In most cases HClO 4 produced better, larger and steeper jumps. In two cases thetitration curves obtained were identical, in two cases better with Electrode 1 andin two cases better with Electrode 2.Summary of the delta pH values (mean value of 3 determinations, delta «pH init»to «pH end»):Solvent HClO 4/El.1 HCl/El.1 HClO 4/El.2 HCl/El.2Ethanol 8.7 9.7 8.7 9.2Acetone 11.9 10.1 11.8 10.4Acetonitrile 13.1 10.7 12.9 10.8Dioxane/IPA 9.1 7.8 9.0 7.9MIBK/glacial acetic acid/toluene6.4 4.3 5.9 4.4Toluene/IPA/H 2O 9.2 7.6 8.7 8.012 Peter Bruttel