| Free Acid or Base |
Molecular Wt |
pKa at 25°C |
| Pyrophosphoric |
177.98 |
0.85 (pKa1) |
| Oxalic |
95.07 |
1.19 (pKa1) |
| Glycerophosphoric |
172.08 |
1.47 (pKa1) |
| Ethylenediamine tetraacetic acid (EDTA) |
292.24 |
1.70 (pKa1) |
| Histidine |
155.16 |
1.82 (pKa1) |
| Pyrophosphoric |
177.98 |
1.96 (pKa2) |
| Maleic |
16.07 |
2.00 (pKa1) |
| Benzenehexacarboxylic (mellitic) |
342.17 |
2.08 (pKa1) |
| Phosphoric |
98.0 0 |
2.12 (pKa1) |
| Brucine tetrahydrate |
466.53 |
2.30 (pKa1) |
| Benzenepentacarboxylic |
296.18 |
2.34 (pKa1) |
| Glycine |
75.07 |
2.34 (pKa1) |
| Benzene-1,2,4,5-tetracarboxylic (pyromellitic) |
254.15 |
2.43 (pKa1) |
| Benzenehexacarboxylic (mellitic) |
342.17 |
2.46 (pKa2) |
| EDTA |
292.24 |
2.60 (pKa2) |
| Malonic |
146.02 |
2.85 (pKa1) |
| Phthalic |
116.13 |
2.90 |
| Benzenepentacarboxylic |
298.16 |
2.95 (pKa2) |
| Salicylic |
138.12 |
2.98 |
| Benzene-1,2,3-tricarboxylic (hemimellitic) |
246.18 |
2.98 (pKa1) |
| 1,4-Piperazinebis-(ethanesulfonic acid) "PIPES" |
302.37 |
3.00 (pKa3) |
| Tartaric |
150.09 |
3.02 (pKa1) |
| Fumaric |
116.07 |
3.03 (pKa1) |
| Glycylglycine |
132.12 |
3.06 |
| Citric acid |
192.12 |
3.06 (pKa1) |
| Cyclopentanetetra-1,2,3,4-carboxylic |
246.17 |
3.07 (pKa1) |
| o-Phthalic |
166.13 |
3.10 (pKa1) |
| Benzene-1,2,4,5-tetracarboxylic (pyromellitic) |
254.15 |
3.13 (pKa2) |
| Benzene-1,3,5-tricarboxylic (trimesic) |
210.14 |
3.16 (pKa1) |
| Benzenehexacarboxylic (mellitic) |
342.17 |
3.24 (pKa3) |
| Dimethylmalonic |
132.12 |
3.29 (pKa1) |
| Mandelic |
152.15 |
3.36 |
| Butane-1,2,3,4-tetracarboxylic |
234.12 1 |
3.36 (pKa) |
| Malic |
134.09 |
3.40 (pKa1) |
| I,l-Cyclohexanediacetic |
200.18 |
3.52 (pKal) |
| 2-Methylpropane-1,2,3-triscarboxylic |
190.15 |
3.53 (pKal) |
| Hippuric |
179.18 |
3.64 |
| Propane-1,2,3-tricarboxylic (tricarballylic) |
176.12 |
3.67(pKa1) |
| Formic |
46.02 |
3.75 |
| 3,3-Dimethylglutaric |
160.17 |
3.79 (pKal) |
| I,l-Cyclopentanediacetic |
186.21 |
3.82 (pKa1) |
| Itaconic |
130.1 |
3.84 (pKa1) |
| Lactic |
90.08 |
3.86 |
| Benzenepentacarboxylic |
298.16 |
3.94 (pKa3) |
| Benzene-1,3,5-tricarboxylic (trimesic) |
210.14 |
3.98 (pKa2) |
| Barbituric |
128.09 |
3.98 |
| Ascorbic |
176.12 |
4.10 (pKa1) |
| 2,2-Dimethflsuccinic |
146.14 |
4.11 (pKa1) |
| Succinic |
118.09 |
4.19 (pKa1) |
| Benzoic |
122.12 |
4.20 |
| Oxalic |
95 07 |
4.21 (pKa2) |
| Benzene-1,2,3-tricarboxylic (hemimellitic) |
246.18 |
4.25 (pKa2) |
| 3,6-Endomethylene-1,2,3,6-tetrahydrophthalic acid "EMTA" |
183.62 |
4.30 (pKa1) |
| 2,2-Dimethylglutaric |
160.17 |
4.31 (pKa1) |
| Butane-1,2,3,4-tetracarboxylic |
234.12 |
4.38 (pKa2) |
| Benzenehexacarboxylic (mellitic) |
342.17 |
4.44 (pKa4) |
| Benzene-1,2,4,5-tetracarboxylic (pyromellitic) |
254.15 |
4.44 (pKa3) |
| Fumaric |
116.07 |
4.47 (pKa2) |
| Cyclopentanetetra-1,2,3,4-carboxylic |
246.17 |
4.48 (pKa2) |
| Tartaric |
150.09 |
4.54 (pKa2) |
| Citric |
210.14 |
4.74 (pKa2) |
| Acetic |
60.05 |
4.76 |
| n-Butyric |
88.1 0 |
4.82 |
| Propane-1,2,3-tricarboxylic (tricarballylic) |
176.12 |
4.84 (pKa2) |
| Benzene-1,3,5-tricarboxylic (trimesic) |
210.14 |
4.85 (pKa3) |
| Propionic |
74.08 |
4.87 |
| 2-Methylpropane-1,2,3-triscarboxylic |
190.15 |
5.02 (pKa2) |
| Malic |
134.09 |
5.05 (pKa2) |
| Benzenepentacarboxylic |
298.16 |
5.07 (pKa4) |
| Pyridine |
79.1 |
5.23 |
| o-Phthalic |
116.13 |
5.27 (pKa2) |
| Citric |
192.12 |
5.40 (pKa3) |
| Butane-1,2,3,4-tetracarboxylic |
234.12 |
5.45 (pKa3) |
| Benzenehexacarboxylic (mellitic) |
342.17 |
5.50 (pKa5) |
| 2,2-Dimethylglutaric |
160.17 |
5.51 (pKa2) |
| Itaconic |
130.1 |
5.55 (pKa2) |
| Cyclopentanetetra-1,2,3,4-carboxylic |
246.17 |
5.57 (pKa3) |
| Succinic |
118.09 |
5.57 (pKa2) |
| Benzene-1,2,4,5-tetracarboxylic (pyromellitic) |
254.15 |
5.61 (pKa4) |
| Benzene-1,2,3-tricarboxylic (hemimellitic) |
246.18 |
5.87 (pKa3) |
| Dimethylmalonic |
132.12 |
5.98 (pKa2) |
| Histidine |
156.16 |
6.00 (pKa2) |
| Hydroxylamine |
34.0 |
6.03 |
| Carbonic (H2CO3+C02) |
62(C02) |
6.10 (pKa1) |
| Malonic |
104.06 |
6.10 (pKa2) |
| 2-(N-Morpholino)-ethane sulfonic acid "MES" |
195.2 |
6.15 (pKa2) |
| Glycerophosphoric |
172.08 |
6.19 (pKa2) |
| Propane-1,2,3-tricarboxylic (tricarballylic) |
176.12 |
6.20(pKa3) |
| Benzenepentacarboxylic |
298.16 |
6.25 (pKa5) |
| Maleic |
116.07 |
6.26 (pKa2) |
| 2,2-Dimethylsuccinic |
146.14 |
6.29 (pKa2) |
| EDTA |
292.24 |
6.30 (pKa3) |
| 3,3-Dimethylglutaric |
160.17 |
6.31 (pKa2) |
| Bis(2-hydroxyethyl)imino-tris(hydroxymethyl) methane "BIS-TRIS" |
209.24 |
6.46 |
| Benzenehexacarboxylic (mellitic) |
342.17 |
6.59 (pKa6) |
| N-(2-Acetamido)imino-diacetic acid "ADA" |
190.17 |
6.60 (pKa3) |
| Butane-1,2,3,4-tetracarboxylic |
234.12 |
6.63 (pKa4) |
| Pyrophosphoric |
177.98 |
6.68 (pKa3) |
| I,l-Cyclopentanediacetic (3,3 tetramethylene glutaric acid) |
186.21 |
6.70 (pKa2) |
| 1,4-Piperazinebis-(ethanesulfonic acid) "PIPES" |
302.37 |
6.8 (pKa4) |
| N-(2-Acetamido)-2-aminoethanesulfonic acid "ACES" |
182.20 |
6.9 (pKa2) |
| I,l-Cyclohexanediacetic |
200.18 |
6.94 (pKa2) |
| 3,6-Endomethylene- 1,2,3,6-tetrahydrophthalicacid "EMTA" |
183.62 |
7.00 (pK2) |
| Imidazole |
68.08 |
7.00 |
| 2-(Aminoethyl)trimethylammonium chloride "CHOLAMINE" |
156.69 |
7.10 |
| N,N-Bis(2-hydroxyethyl)-2-aminoethanesulfonic acid "BES" |
213.25 |
7.15 (pKa2) |
| 2-Methylpropane- 1,2,3-triscarboxylic |
190.15 |
7.20 (pKa3) |
| 2-(N-Morpholino)propane-sulfonic acid "MOPS" |
209.27 |
7.20 (pKa2) |
| Phosphoric |
98.0 |
7.21 (pKa2) |
| N-Tris(hydroxymethyl)methyl-2-aminoethane sulfonic acid "TES" |
229.28 |
7.50 (pKa2) |
| N-2-Hydroxyethylpiperazine-N'-2-ethanesulfonic acid "HEPES" |
238.31 |
7.55 (pKa2) |
| 2-Hydroxyethylimino-tris(hydroxymethyl)methane "MONO-TRIS" |
165.18 |
7.83 |
| Brucine tetrahydrate |
466.53 |
7.95 (pKa2) |
| 4-(2-Hydroxyethyl)- I -piperazinepropane sulfonic acid "EPPS" |
252.23 |
8.00 |
| Tris(hydroxymethyl)aminomethane"TRIS" |
121.14 |
8.10 |
| N-Tris(hydroxymethyl)methylglycine "TRICINE" |
180.18 |
8.15 |
| Glycinamide |
74.04 |
8.20 |
| N,N-Bis(2-hydroxyethyl)glycine"BICINE" |
163.18 |
8.35 |
| N-Tris(hydroxymethyl)methyl-2-aminopropane sulfonic acid "TAPS" |
243.3 |
8.40 (pKa2) |
| N-Glycyl-glycine |
132.12 |
8.40 |
| Histidine |
155.16 |
9.17 (pKa3) |
| Boric |
43.82 |
9.24 |
| Pyrophosphoric |
177.98 |
9.39 (pKa4) |
| Ethanolamine |
61.08 |
9.44 |
| Glycine |
75.07 |
9.60 (pKa2) |
| Trimethylamine |
59.11 |
9.74 |
| Cyclopentanetetra-1,2,3,4-carboxylic |
246.17 |
10.06 (pKa4) |
| Carbonic (H2CO3 + CO2) |
62(CO2) |
10.25 (pKa2) |
| 3-Cyclohexylamino-l-propanesulfonic acid "CAPS" |
221.32 |
10.40 (pKa2) |
| EDTA |
292.24 |
10.60 (pKa4) |
| Methylamine |
31.06 |
10.64 |
| Dimethylamine |
45.09 |
10.72 |
| Ethylamine |
45.09 |
10.75 |
| Triethylamine |
101.19 |
10.76 |
| Diethylamine |
73.14 |
10.98 |
| Ascorbic |
176.12 |
11.79 (pKa2) |
| Phosphoric |
98.00 |
12.32 (pKa3) |
|
