Monograph - Metrohm

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Titration of basesThe lowest pH values at the end of the titration were:with HClO 4 ; –5.7 in MIBK/glacial acetic acid/toluene/El.1 and –5.5 inacetone/El.1with HCl; –3.7 in MIBK/glacial acetic acid/toluene/El.1 and –3.4 inthe same solvent/El.2Very good solvents for medium-strength bases are acetone, acetonitrileand toluene/IPA/H 2 O.B) Aniline (pK B = 9.42)Except for ethanol the jumps with HClO 4 were larger, steeper and neater. In fourcases the curves were identical with each electrode, in two cases Electrode 1was better (MIBK/glacial acetic acid/toluene and toluene/IPA/H 2 O).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 5.8 5.5 5.7 5.1Acetone 7.0 4.3 7.0 4.4Acetonitrile 7.5 4.8 7.4 4.6Dioxane/IPA 5.2 3.8 5.2 3.9MIBK/glacial acetic acid/toluene5.8 4.0 5.7 4.0Toluene/IPA/H 2O 5.6 3.6 5.3 3.8The lowest pH values at the end of the titration were:with HClO 4 ; –5.6 in MIBK/glacial acetic acid/toluene - El.1 and –5.3in acetone - El.1with HCl; –3.6 in MIBK/glacial acetic acid/toluene - El. 1 and –3.2in the same solvent - El.2Very good solvents for weak bases are acetone, MIBK/glacial acetic acid/toluene and also ethanol.C) Urea (pK B = 13.80)This very weak base could not be determined in any of the solvents tested. Notitration curves that could be evaluated were obtained!Non-aqueous titration of acids and bases with potentiometric endpoint indication 13
pK Avalues of some selected acids7 pK A values of some selected acidsAcetic acid .......................................... 4.73Acrylic acid ......................................... 4.26o-Aminophenol ................................. 10.68Benzoic acid ....................................... 4.20Boric acid ........................................... 9.24Chloroacetic acid ............................... 2.81o-Chlorophenol .................................. 8.48Citric acid 1 st step .............................. 3.13Citric acid 2 nd step .............................. 4.76Citric acid 3 rd step .............................. 6.40Dichloroacetic acid ............................. 1.30Fluoroacetic acid ................................ 2.57Formic acid ........................................ 3.75Glycolic acid ....................................... 3.82Hydrobromic acid ..................... approx. –6Hydrochloric acid ..................... approx. –3Hydrocyanic acid ................................ 9.40Hydrofluoric acid ................................ 3.14Hydrosulphuric acid 1 st step ............... 6.90Hydrosulphuric acid 2 nd step ............ 12.90m-Hydroxybenzoic acid ..................... 4.08o-Hydroxybenzoic acid ...................... 2.98p-Hydroxybenzoic acid ...................... 4.54Lactic acid .......................................... 3.86Malonic acid 1 st step .......................... 2.79Malonic acid 2 nd step .......................... 5.68Nitric acid ......................................... –1.32o-Nitrophenol ..................................... 7.23Oxalic acid 1 st step ............................. 1.42Oxalic acid 2 nd step ............................ 4.31Perchloric acid ......................... approx. –9Phenol ................................................ 9.95Phosphoric acid 1 st step ..................... 1.96Phosphoric acid 2 nd step .................... 7.12Phosphoric acid 3 rd step .................. 12.36o-Phthalic acid 1 st step ....................... 2.90o-Phthalic acid 2 nd step ...................... 5.51Picric acid ........................................... 0.71Propionic acid .................................... 4.87Salicylic acid ...................................... 2.98Sorbic acid ......................................... 4.77Succinic acid 1 st step ......................... 4.18Succinic acid 2 nd step ......................... 5.55Sulphuric acid 1 st step .............. approx. –3Sulphuric acid 2 nd step ....................... 1.92Tartaric acid 1 st step ........................... 3.01Tartaric acid 2 nd step .......................... 4.16Trichloroacetic acid ............................ 0.70Trifluoroacetic acid ............................. 0.2314 Peter Bruttel
Page 1 and 2: MonographNon-aqueous titration of a
Page 3 and 4: ContentsContents1. Preface ........
Page 5 and 6: Important terms2 Important termsAmp
Page 7 and 8: Remarks concerning solvents for non
Page 9 and 10: Remarks concerning solvents for non
Page 11 and 12: Titration of acidsResultsA) Benzoic
Page 13: Titration of bases6 Titration of ba
Page 17 and 18: Dielectric constants (DC) of some s
Page 19 and 20: Compilation of results: bases as ti
Page 25 and 26: Standard deviations of the electrod
Page 27 and 28: Titration curves obtained with the
Page 39 and 40: Compilation of results: acids as ti
Page 45 and 46: Standard deviations of the electrod
Page 57: Titration curves obtained with the

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