Monograph
Non-aqueous titration of acids and bases
with potentiometric endpoint indication
Peter Bruttel
Non-aqueous titration of acids and bases
with potentiometric endpoint indication
Peter Bruttel
All rights reserved, including translation rights.
Printed in Switzerland by Metrohm Ltd., CH-9101 Herisau
08.1999 – 8.024.5003
Non-aqueous titration of acids and bases with potentiometric endpoint indication
Contents
Contents
1.
Preface ................................................................................................... 3
2.
Important terms ...................................................................................... 4
3.
Remarks concerning solvents for non-aqueous titrations ....................... 5
4.
Apparatus and accessories used ........................................................... 9
5.
Titration of acids ..................................................................................... 9
6.
Titration of bases .................................................................................. 12
7.
pKA values of some selected acids ....................................................... 14
8.
pKB values of some selected bases ...................................................... 15
9.
Dielectric constants (DC) of some selected solvents ............................ 16
10.
Literature references ............................................................................ 17
Compilation of results: bases as titrants ......................................................... 18
Standard deviations of the electrode signals ........................................ 24
Titration curves obtained with the Solvotrode
LiCl sat. in ethanol ........................................................................... 25
0.4 mol/L TEA-Br in ethylene glycol ................................................ 31
Compilation of results: acids as titrants .......................................................... 37
Standard deviations of the electrode signals ........................................ 44
Titration curves obtained with the Solvotrode
LiCl sat. in ethanol ........................................................................... 45
0.4 mol/L TEA-Br in ethylene glycol ................................................ 49
2
Peter Bruttel
Preface
1 Preface
Non-aqueous titrations continue to play an important role in analysis, no matter
whether in the determination of acid or base numbers in oils and fats, for quantifying products with different acidic or basic strengths separately or for titrating
substances that are insoluble in water.
This monograph is not intended to be a textbook; it should rather help the practical chemist to decide which solvents, electrodes, titrants and instruments are the
most suitable ones for the particular application. The monograph makes no claim
to be complete; it also assumes a certain basic knowledge of potentiometric
analysis.
Non-aqueous titrations are not without their problems. Effects are experienced
that do not occur in this form in purely aqueous systems. The main problems are:
a) interferences caused by static electricity and
b) the response behaviour of the electrodes used.
As far as a) is concerned a wide range of different measures have already been
introduced or at least tried. These include everything from titration in earthed
solutions through shielding the complete titration system (Faraday cage) and up
to the use of differential amplifiers and the three-electrode technique. This latter
technique has its advantages in many cases, above all wherever work is carried
out in nonpolar solvents with nonpolar samples (e.g. petrochemical products).
The type of electrode(s) used also plays a major role, which brings us to point b).
Many years of experience involving non-aqueous titration have resulted in
Metrohm developing a special electrode that is particularly suitable for non-aqueous titration – the 6.0229.100 Solvotrode. It meets all the demands that must be
placed on such an electrode: large membrane surface, as small a membrane
resistance as possible, rapid response, optimally designed ground-joint diaphragm, excellent shielding and appropriate electrolyte solutions.
Non-aqueous titration of acids and bases with potentiometric endpoint indication
3
Important terms
2 Important terms
Amphiprotic
Appreciable self-dissociation (e.g. 2 CH3OH <
as polar.
>
CH3OH2+ + CH3O– ), also known
Aprotic
No self-dissociation, also known as nonpolar.
Dielectric constant (DC)
Proportionality factor between the electric displacement D and the electric field
strength E in a vacuum. The DC depends strongly on temperature. Solvents with
a higher DC promote the electrolytic dissociation of electrolytes. The DC is a
substance-specific constant that depends to a large extent on the molecular structure. It is measured with so-called decameters. In nonpolar solvents (having a
small DC) even strong electrolytes (e.g. NaCl, HClO4, etc.) are only weakly dissociated.
Dissociation
Formation of ions, e.g. CH3COOK
<
> CH3COO– + K+
Levelling
Equalising of base or acid strengths. In this case separation is not possible. Example: sulphuric acid:
During the titration, e.g. in acetone, two well-differentiated steps are obtained. In
an aqueous titration levelling occurs; only one potential jump is obtained, which
corresponds to the sum of the two acids of different strengths.
pK value
Acidity or basicity constants
KA = [H3O+] [A–] / [HA]
KB = [BH+] [OH–] / [B]
The negative logarithms of these values are known as pKA and pKB, respectively;
they are analogous to the pH value. The smaller the value, the «stronger» the
acid or base. In order to achieve a separation in an aqueous titration the difference between the pK values should be approx. 5. In suitable non-aqueous solvents a difference of 2 to 3 is sufficient.
4
Peter Bruttel
Remarks concerning solvents for non-aqueous titrations
3 Remarks concerning solvents for non-aqueous titrations
3.1 Amphiprotic solvents – acidic
3.1.1 Glacial acetic acid (HAc)
Solvent for bases in particular. The water content should be less than 1%. In
some cases acetic anhydride is added. However, this can lead to acetylation and
therefore to incorrect results (primary, secondary and tertiary amines). For the
titration of weak bases it is better to add an aprotic solvent, e.g. dioxane or toluene.
3.1.2 Formic acid
Is only used for the titration of the weakest bases, e.g. caffeine (pKB = 13.4) or
urea (pKB = 13.8). The water content should not exceed 1%. Should not be used
with short-chain alcohols – esterification!
3.1.3 Trifluoroacetic acid
Suitable as a solvent for the weakest bases, where acetic anhydride cannot be
used because of acetylation. An expensive solvent!
3.1.4 Others
Propionic acid, cresols and phenol are not very important. Cresols are used in
mixtures, e.g. with chloroform, as solvents for determinations of terminal amino
groups in polyamides. As phenol has excellent solubilising properties for the
salts of organic bases, its use with a mixture of chloroform and acetonitrile has
been suggested for these applications.
3.2 Amphiprotic solvents – basic
3.2.1 Ethylenediamine
Used as a solvent for weak acids. Has good solubilising properties. Has a levelling effect for strong acids – carboxylic acids and phenols can nevertheless be
separated. It fumes when exposed to the air, is toxic and corrosive and also has
an unpleasant odour. Takes up water and carbon dioxide from the air (blank values).
3.2.2 Butylamine
Similar properties to ethylene diamine, but has slightly smaller solubilising properties. Offensive odour.
3.2.3 Benzylamine
If it has to be a solvent from this class (3.2), then this one. Similar to butylamine,
but better solubilising properties and less offensive odour.
Non-aqueous titration of acids and bases with potentiometric endpoint indication
5
Remarks concerning solvents for non-aqueous titrations
3.3 Amphiprotic solvents – neutral
3.3.1 Methanol and ethanol
Compared with water they have lower dielectric constants but similar acidity and
basicity. Not suitable for the determination of weak acids such as phenol. However, the carboxyl groups of dicarboxylic acids and the two acid groups of sulphuric acid can be separated. They also have certain solubilising properties for
organic compounds that water does not possess.
3.3.2 Isopropanol
Has excellent solubilising properties, e.g. for hydrocarbons, and is often used as
a solubility promoter between these and water. As a secondary alcohol it is a
weaker «acid» than the primary alcohols and can be used instead of them without any problems. The determination of weak acids is also not possible in this
solvent.
3.3.3 tert. Butanol
Unfortunately has a relatively high melting point of 25.8 °C. Approx. 5% isopropanol (IPA) should therefore be added. Tertiary alcohols can almost be classified
as being aprotic solvents. Has no levelling properties and is therefore particularly
suitable for the step-by-step titration of mixtures of acids – up to the phenols.
3.3.4 Diols (ethylene glycol/propylene glycol)
Particularly suitable as solvents for the salts of weak acids because of their high
polarity. However, mostly used in 1:1 mixtures with chloroform, toluene or IPA.
3.3.5 Ethylene glycol monomethyl ether (methylglycol, methylcellosolve)
Can be used for the titration of weak bases and has good solubilising properties.
Is used together with acetic anhydride for the determination of small amounts of
quaternary amines in other amines (the other amines are acetylated and are
therefore not determined).
3.4 Aprotic solvents – acidic
3.4.1 Nitromethane and nitroethane
As a result of their high polarity, which favours the dissociation of salts, both
would be very useful solvents for the titration of weak bases. Unfortunately both
present explosion and fire hazards and are therefore seldom used. A special
application would be the titration of mixtures of primary, secondary and tertiary
aliphatic or aromatic amines in a solvent mixture made up of glacial acetic acid/
dioxane/nitromethane at a ratio of 5:75:20.
6
Peter Bruttel
Remarks concerning solvents for non-aqueous titrations
3.5 Aprotic solvents – basic
3.5.1 Pyridine
Were it not for its unpleasant odour and its harmful side-effects this solvent would
be particularly suitable for the separation of mixtures of acids. Levelling occurs
only with strong mineral acids (HCl, HClO4, 1st proton of H2SO4). Otherwise acids
up to phenol can be separated. A particular use of pyridine is for the determination of polyacids. A special advantage is that pyridine does not undergo any side
reactions with strong acids, which allows exact determinations to be carried out.
3.5.2 Dimethylformamide (DMF)
DMF is an excellent solvent for polar compounds, is not toxic and also has no
odour. Can be used for the determination of weak acids, but only when water is
almost completely absent (saponification). Unfortunately has a relatively high
reactivity, which prevents the determination of mixtures that contain strong acids
(errors of up to 20%). Mixtures containing alcohols are also unfavourable as the
titration curves become extremely flat (also with alcoholic titrants).
3.5.3 Dimethylsulphoxide (DMSO)
Similar properties to DMF, without its tendency to saponify. Warning: DMSO reacts violently with HClO4!!!!
3.6 Aprotic solvents – neutral
3.6.1 Acetone and MIBK
The ideal solvents for mixtures of acids, from HClO4 up to phenol. Practically no
levelling occurs. Absorption of CO2 from the air takes place so slowly that, if need
be, the titration can be carried out in an open beaker.
3.6.2 Acetonitrile
Is used for the determination of basic amines having different basicities. Acids
can also be separated. Acetates of Cu, Ni, etc. can be titrated in this solvent; this
may be due to the formation of complexes.
3.6.3 Nitrobenzene
Would give an excellent differentiation of amines having different basicities, but
should not be used because of its toxicity.
Non-aqueous titration of acids and bases with potentiometric endpoint indication
7
Remarks concerning solvents for non-aqueous titrations
3.6.4 Ethers (diethyl ether, dioxane, tetrahydrofuran, ethylene glycol
dimethyl ether)
Mostly only used for dilution purposes. HClO4 in dioxane is used as a titrant.
Ethers often contain peroxides, which can react like acids during the titration. In
pure dioxane and diethyl ether no potentiometric indication is possible – the resistance is too high. Even a differential amplifier does not help. If these solvents
have to be used, then for weak bases.
3.6.5 Hydrocarbons and chlorinated hydrocarbons
Examples: hexane, benzene, toluene, chlorobenzene, trichloroethylene, chloroform, tetrachloroethane, etc.
Mostly only used for diluting or dissolving. Solvents such as benzene and chlorobenzene are very questionable. Chlorinated hydrocarbons are disappearing more
and more from the specifications. In pure solvents of this class the endpoint
cannot be indicated potentiometrically or conductometrically. Only colour indicators can be used.
3.6.6 Acetic anhydride
Is used for the removal of residual water in the titration of extremely weak bases
(e.g. thiourea, acetylpiperidine). The acetyl ion is an even stronger acid than the
acetonium ion (CH3COOH2+).
CH3COOCOCH3 + HClO4 → CH3CO+ + ClO4– + CH3COOH
The acetyl cation is extremely reactive. Primary, secondary and tertiary amines
are acetylated and therefore removed from the titration. It is possible to determine quaternary amines in the presence of all the other amines. The presence of
more than 10% acetic acid reduces the titrability of weak bases by buffering.
Gel layers on glass electrodes are rapidly dehydrated; this results in a sluggish
response.
8
Peter Bruttel
Apparatus and accessories used – Titration of acids
4 Apparatus and accessories used
- 702, 716, 736, 751 or 785 Titrino or 726 Titroprocessor, 728 Magnetic stirrer,
Metrodata TiNet software, printer and PC
- 6.3014.223 Exchange Units
- 6.0229.100 Solvotrode*; electrolyte a) 6.2312.000 LiCl sat. in ethanol, electrolyte b) 6.2320.000 TEA-Br 0.4 mol/L in ethylene glycol
5 Titration of acids
The 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).
Electrodes
1) 6.0229.100 Solvotrode, electrolyte LiCl sat. in ethanol
2) 6.0229.100 Solvotrode, electrolyte TEA-Br c = 0.4 mol/L in ethylene glycol
(TEA-Br = tetraethyl ammonium bromide)
Acids tested (0.1 mol/L in ethanol)
- Benzoic acid; pKA = 4.20
- Phenol; pKA = 9.95
Titrants
a) c(TBAOH) = 0.1 mol/L in IPA (TBAOH = tetrabutyl ammonium hydroxide, IPA
= isopropanol)
b) c(KOH) = 0.1 mol/L in IPA
Solvents
Ethanol
Isopropanol (IPA)
tert. Butanol/IPA 95:5
Acetone
Methyl isobutyl ketone (MIBK)
Dimethyl formamide (DMF)
Pyridine
Acetonitrile
2.50 mL of the tested acid was treated with 50 mL of the corresponding solvent
and titrated with TBAOH or KOH.
*
The Solvotrode is a combined pH glass electrode developed specially for non-aqueous
titrations.
** The concept of pH really applies only to purely aqueous solutions. In organic solvents the
values are displaced. The neutral point is no longer at «pH = 7» and negative values or values
up to 20 can occur (extension of the pH scale). This means that at «high» pH values high
alkali errors must be expected with glass electrodes.
Non-aqueous titration of acids and bases with potentiometric endpoint indication
9
Titration of acids
Results
A) Benzoic acid (pKA = 4.20)
KOH normally produces larger potential jumps than TBAOH, but TBAOH yields
more symmetrical and steeper titration curves. In 11 (63%) out of 16 determinations larger jumps were obtained with Electrode 2 (underlined values).
Summary of the delta pH values (mean value of 3 determinations, delta «pH init»
to «pH end»):
Solvent
KOH/El.1
TBAOH/El.1
KOH/El.2
TBAOH/El.2
Ethanol
7.6
7.3
8.1
7.5
IPA
8.5
7.1
8.7
8.5
tert. Butanol/IPA
8.9
9.5
8.2
8.9
Acetone
9.0
6.4
8.1
7.6
MIBK
7.7
7.6
7.1
7.0
DMF
7.6
5.8
8.7
6.5
Pyridine
6.1
6.1
8.0
7.0
Acetonitrile
7.3
6.7
10.2
7.7
The highest pH values at the end of the titration were:
with KOH; 18.2 in DMF/El.2, 16.8 in DMF/El.1 and in pyridine/El.2
with TBAOH; 16.0 in pyridine/El.2, 15.9 in tert. butanol/El.2
The lowest pH values at the end of the titration were:
with KOH; 11.6 in ethanol/El.1, 12.4 in MIBK/El.1
with TBAOH; 11.1 in ethanol/El.1, 11.7 in MIBK/El.1
Li ions therefore appear to have a certain influence on the pH value (alkali error).
The largest jump was obtained with KOH/El.2 in acetonitrile (delta pH = 10.2).
However, acetonitrile is a problematic solvent. During the titration sticky precipitates formed with both titrants, which lead to blockage of the diaphragm. This
means that with this solvent the electrode should be cleaned after each titration
(H2O and ethanol).
Very good solvents for medium-strength acids are tert. butanol/IPA, acetone, DMF and isopropanol (IPA).
B) Phenol (pKA = 9.95)
With TBAOH as titrant the endpoint is normally reached sooner. Electrode 2 usually gives titration curves that are easier to evaluate.
10
Peter Bruttel
Titration of acids
Summary of the delta pH values (mean value of 3 determinations, delta «pH init»
to «pH end»):
Solvent
KOH/El.1
TBAOH/El.1
KOH/El.2
TBAOH/El.2
Ethanol
3.7 —
3.3 —
3.8 —
3.3 —
4.4 -
3.8 +
5.0 +
4.9 +
IPA
tert. Butanol/IPA
4.6 -
4.3 +
4.6 +
6.8 ++
4.4 ++
3.3 ++
3.9 +
3.9 ++
MIBK
6.0 -
6.0 —
5.7 -
5.6 —
DMF
4.5 ++
3.7 +
5.4 ++
4.3 ++
Pyridine
3.2 +
4.4 ++
5.3 +
4.8 +
Acetonitrile
3.4 +
4.0 ++
5.4 ++
4.1 ++
Acetone
—
+
++
no jump
suggestion of a jump
EP found
pronounced jump, easy to evaluate
In 12 (75%) out of 16 determinations larger jumps were obtained with Electrode
2.
The highest pH values at the end of the titration were:
with KOH; 17.4 in DMF/El.2, 16.4 in pyridine/El.2
with TBAOH; 16.0 in DMF/El.2 and in pyridine/El.2
The lowest pH values at the end of the titration were:
with KOH; 11.6 in ethanol/El.1, 12.8 in MIBK/El.1
with TBAOH; 11.1 in ethanol/El.1, 11.5 in MIBK/El.1
The largest jump was obtained with TBAOH/El.2 in tert. butanol/IPA (delta pH =
6.8). Acetonitrile produced nice curves. Unfortunately sticky precipitates on the
diaphragm were also produced here, which made it necessary to clean the electrode (H2O and ethanol) after each determination.
Very good solvents for weak acids are acetone, DMF and tert. butanol/IPA
(in ethanol no titration curves were obtained; it is too similar to water).
Non-aqueous titration of acids and bases with potentiometric endpoint indication
11
Titration of bases
6 Titration of bases
The 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»
Electrodes
1) 6.0229.100 Solvotrode, electrolyte LiCl sat. in ethanol
2) 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; pKB = 4.56
- Aniline; pKB = 9.42
- Urea; pKB = 13.80
Titrants
a) c(HClO4) = 0.1 mol/L in glacial acetic acid
b) c(HCl) = 0.2 mol/L in isopropanol (IPA)
Solvents
Ethanol
Acetone
Acetonitrile
Dioxane/IPA 1:1
MIBK/glacial acetic acid/toluene 1:1:1 (DIN/ISO 3771)
Toluene/IPA/H2O 500:495:5 (ASTM D 664)
2.50 mL of the tested base was treated with 50 mL of the corresponding solvent
and titrated with HClO4 or HCl.
Results
A) Ethanolamine (pKB = 4.56)
In most cases HClO4 produced better, larger and steeper jumps. In two cases the
titration curves obtained were identical, in two cases better with Electrode 1 and
in two cases better with Electrode 2.
Summary of the delta pH values (mean value of 3 determinations, delta «pH init»
to «pH end»):
Solvent
HClO4/El.1
HCl/El.1
HClO4/El.2
HCl/El.2
Ethanol
8.7
9.7
8.7
9.2
Acetone
11.9
10.1
11.8
10.4
Acetonitrile
13.1
10.7
12.9
10.8
Dioxane/IPA
9.1
7.8
9.0
7.9
MIBK/glacial acetic acid/
toluene
6.4
4.3
5.9
4.4
Toluene/IPA/H2O
9.2
7.6
8.7
8.0
12
Peter Bruttel
Titration of bases
The lowest pH values at the end of the titration were:
with HClO4;
with HCl;
–5.7 in MIBK/glacial acetic acid/toluene/El.1 and –5.5 in
acetone/El.1
–3.7 in MIBK/glacial acetic acid/toluene/El.1 and –3.4 in
the same solvent/El.2
Very good solvents for medium-strength bases are acetone, acetonitrile
and toluene/IPA/H2O.
B) Aniline (pKB = 9.42)
Except for ethanol the jumps with HClO4 were larger, steeper and neater. In four
cases the curves were identical with each electrode, in two cases Electrode 1
was better (MIBK/glacial acetic acid/toluene and toluene/IPA/H2O).
Summary of the delta pH values (mean value of 3 determinations, delta «pH init»
to «pH end»):
Solvent
HClO4/El.1
HCl/El.1
HClO4/El.2
HCl/El.2
Ethanol
5.8
5.5
5.7
5.1
Acetone
7.0
4.3
7.0
4.4
Acetonitrile
7.5
4.8
7.4
4.6
Dioxane/IPA
5.2
3.8
5.2
3.9
MIBK/glacial acetic acid/
toluene
5.8
4.0
5.7
4.0
Toluene/IPA/H2O
5.6
3.6
5.3
3.8
The lowest pH values at the end of the titration were:
with HClO4;
with HCl;
–5.6 in MIBK/glacial acetic acid/toluene - El.1 and –5.3
in acetone - El.1
–3.6 in MIBK/glacial acetic acid/toluene - El. 1 and –3.2
in the same solvent - El.2
Very good solvents for weak bases are acetone, MIBK/glacial acetic acid/
toluene and also ethanol.
C) Urea (pKB = 13.80)
This very weak base could not be determined in any of the solvents tested. No
titration curves that could be evaluated were obtained!
Non-aqueous titration of acids and bases with potentiometric endpoint indication
13
pKA values of some selected acids
7 pKA values of some selected acids
Acetic acid .......................................... 4.73
Malonic acid 2nd step .......................... 5.68
Acrylic acid ......................................... 4.26
Nitric acid ......................................... –1.32
o-Aminophenol ................................. 10.68
o-Nitrophenol ..................................... 7.23
Benzoic acid ....................................... 4.20
Oxalic acid 1st step ............................. 1.42
Boric acid ........................................... 9.24
Oxalic acid 2nd step ............................ 4.31
Chloroacetic acid ............................... 2.81
Perchloric acid ......................... approx. –9
o-Chlorophenol .................................. 8.48
Phenol ................................................ 9.95
Citric acid 1 step .............................. 3.13
Phosphoric acid 1st step ..................... 1.96
Citric acid 2 step .............................. 4.76
Phosphoric acid 2nd step .................... 7.12
Citric acid 3rd step .............................. 6.40
Phosphoric acid 3rd step .................. 12.36
Dichloroacetic acid ............................. 1.30
o-Phthalic acid 1st step ....................... 2.90
Fluoroacetic acid ................................ 2.57
o-Phthalic acid 2nd step ...................... 5.51
Formic acid ........................................ 3.75
Picric acid ........................................... 0.71
Glycolic acid ....................................... 3.82
Propionic acid .................................... 4.87
Hydrobromic acid ..................... approx. –6
Salicylic acid ...................................... 2.98
Hydrochloric acid ..................... approx. –3
Sorbic acid ......................................... 4.77
Hydrocyanic acid ................................ 9.40
Succinic acid 1st step ......................... 4.18
Hydrofluoric acid ................................ 3.14
Succinic acid 2nd step ......................... 5.55
Hydrosulphuric acid 1 step ............... 6.90
Sulphuric acid 1st step .............. approx. –3
Hydrosulphuric acid 2nd step ............ 12.90
Sulphuric acid 2nd step ....................... 1.92
m-Hydroxybenzoic acid ..................... 4.08
Tartaric acid 1st step ........................... 3.01
o-Hydroxybenzoic acid ...................... 2.98
Tartaric acid 2nd step .......................... 4.16
p-Hydroxybenzoic acid ...................... 4.54
Trichloroacetic acid ............................ 0.70
Lactic acid .......................................... 3.86
Trifluoroacetic acid ............................. 0.23
st
nd
st
Malonic acid 1st step .......................... 2.79
14
Peter Bruttel
pKB values of some selected bases
8 pKB values of some selected bases
Acridine .............................................. 9.89
Ethylenediamine 2nd step ................... 7.00
m-Aminobenzoic acid ...................... 10.92
Imidazole ............................................ 7.00
o-Aminobenzoic acid ....................... 11.85
Methylamine ...................................... 3.36
p-Aminobenzoic acid ....................... 11.64
α-Naphthylamine ............................. 10.08
Ammonia ............................................ 4.75
o-Nitroaniline .................................... 14.13
Aniline ................................................ 9.42
o-Phenylenediamine 1st step ............. 9.53
Benzidine 1st step ............................... 9.30
o-Phenylenediamine 2nd step .............. >12
Benzidine 2 step ............................ 10.37
2-Picoline ........................................... 7.52
Benzimidazole .................................... 8.47
Piperazine 1st step ............................. 4.18
Benzylamine ...................................... 4.62
Piperazine 2nd step ............................. 8.32
Brucine ............................................... 3.10
Piperidine ........................................... 2.80
Caffeine ............................................ 13.39
n-Propylamine .................................... 3.42
Collidine ............................................. 6.69
Pyridine .............................................. 8.81
Cyclohexylamine ................................ 3.36
Pyrimidine .......................................... 1.30
Diethanolamine .................................. 5.12
Quinine 1st step .................................. 6.66
Diethylamine ...................................... 3.00
Quinine 2nd step ................................. 9.48
Dimethylamine ................................... 3.30
o-Toluidine .......................................... 9.61
Diphenylamine ................................... 8.79
Triethanolamine ................................. 6.23
Ethanolamine ..................................... 4.56
Triethylamine ...................................... 3.28
Ethylamine ......................................... 3.33
Trimethylamine ................................... 4.20
Ethylenediamine 1 step .................... 3.91
Urea ................................................. 13.80
nd
st
Non-aqueous titration of acids and bases with potentiometric endpoint indication
15
Dielectric constants (DC) of some selected solvents
9 Dielectric constants (DC) of some selected solvents
Acetic acid ............................... 6.2 (20 °C)
DMF ...................................... 27.0 (25 °C)
Acetone ................................. 21.2 (20 °C)
Ethanol .................................. 25.1 (20 °C)
Acetonitrile ............................ 36.0 (20 °C)
Ethylene glycol ...................... 38.7 (20 °C)
Benzyl alcohol ....................... 13.0 (20 °C)
Ethylenediamine ................... 12.9 (25 °C)
tert. Butanol .......................... 10.9 (30 °C)
Formic acid ........................... 58.5 (25 °C)
Butylamine .............................. 5.3 (25 °C)
Isopropanol ........................... 19.0 (20 °C)
Carbon tetrachloride ............... 2.2 (20 °C)
Methanol ............................... 33.6 (20 °C)
Chlorobenzene ........................ 5.6 (25 °C)
MIBK ..................................... 18.5 (25 °C)
Cyclohexane ........................... 2.0 (20 °C)
Phenol ..................................... 9.7 (48 °C)
Cyclohexanol ........................ 16.8 (25 °C)
Pyridine ................................. 13.5 (20 °C)
Diethyl ether ............................ 4.2 (25 °C)
Toluene .................................... 2.4 (20 °C)
Dioxane ................................... 2.2 (25 °C)
Water ..................................... 80.4 (20 °C)
16
Peter Bruttel
Literature references
10 Literature references
Gyenes, I.
Titration in Non-Aqueous Media
Krieger Publishing Company 1968 (ISBN 0442329253)
Huber, W.
Titrationen in nichtwässrigen Lösungsmitteln (Titrations in non-aqueous
solvents; in German)
Akademische Verlagsgesellschaft, Frankfurt a.M. 1964
Stammbach, K.
Titrationen in nichtwässrigen Lösungsmitteln (Titrations in non-aqueous
solvents; in German)
SLZ (reprint) dated 1969/1970
Oehme, F., Richter, W.
Instrumental Titration Techniques
Hüthig Verlag, Heidelberg 1987 (ISBN 3-7785-1304-4)
Metrohm Monograph «Practical Aspects of Modern Titration»
Metrohm Monograph «Electrodes in Potentiometry»
Metrohm Application Bulletins:
No. 39
Potentiometric analysis of nitrating acid
No. 68
Potentiometric determination of carboxyl and amino end groups in
polyamide fibres
No. 80
Determination of the acid/base number in petroleum products (TAN/
TBN)
No. 175
Non-aqueous titrations of fatty acids in heptane extracts
No. 200
Determination of the acid number, the hydroxyl number and the isocyanates in plastic materials through automatic potentiometric titration
No. 206
Titre determinations in potentiometry
Non-aqueous titration of acids and bases with potentiometric endpoint indication
17
Compilation of results: bases as titrants
Compilation of results: bases as titrants
a) Electrode with LiCl sat. in ethanol
b) Electrode with TEA-Br in ethylene glycol
I. Benzoic acid; titrant: KOH in IPA
Solvent
Electr.
pH init
pH end
d pH
pH EP
«TAN»
Ethanol
a)
3.9
11.9
8.0
8.65
0.104
Ethanol
a)
4.2
11.6
7.4
8.73
0.102
Ethanol
a)
4.2
11.7
7.5
9.00
0.104
Ethanol
b)
4.5
12.5
8.0
9.13
0.106
Ethanol
b)
4.5
12.5
8.0
9.10
0.104
Ethanol
b)
4.5
12.8
8.3
9.12
0.104
Isopropanol
a)
5.0
13.5
8.5
9.63
0.106
Isopropanol
a)
5.2
13.6
8.4
9.42
0.105
Isopropanol
a)
5.0
13.6
8.6
9.59
0.108
Isopropanol
b)
6.0
14.2
8.2
10.02
0.108
Isopropanol
b)
5.6
14.2
8.6
10.56
0.106
Isopropanol
b)
4.5
13.8
9.3
10.39
0.112
Tert. butanol
a)
5.5
14.4
8.9
10.76
0.111
Tert. butanol
a)
5.9
14.6
8.7
10.65
0.111
Tert. butanol
a)
5.4
14.6
9.2
10.56
0.109
Tert. butanol
b)
6.4
14.8
8.4
10.58
0.116
Tert. butanol
b)
6.5
14.7
8.2
10.38
0.112
Tert. butanol
b)
6.6
14.7
8.1
10.27
0.112
Acetone
a)
5.3
14.0
8.7
10.98
0.104
Acetone
a)
5.5
14.7
9.2
10.38
0.105
Acetone
a)
6.5
15.6
9.1
10.38
0.104
Acetone
b)
8.0
15.9
7.9
11.50
0.104
Acetone
b)
8.2
16.1
7.9
11.73
0.104
Acetone
b)
7.3
15.8
8.5
11.13
0.104
MIBK
a)
5.9
13.6
7.7
9.83
0.117
MIBK
a)
6.0
13.5
7.5
9.77
0.116
MIBK
a)
5.9
13.7
7.8
9.82
0.116
MIBK
b)
5.7
12.5
6.8
7.73
0.116
MIBK
b)
5.6
12.4
6.8
7.96
0.115
MIBK
b)
7.1
14.7
7.6
9.81
0.116
DMF
a)
8.1
16.8
8.7
12.38
0.118
DMF
a)
8.4
16.0
7.6
11.33
0.117
DMF
a)
8.3
15.8
7.5
11.34
0.120
18
Remarks
Peter Bruttel
Compilation of results: bases as titrants
Solvent
Electr.
pH init
pH end
d pH
pH EP
«TAN»
DMF
b)
8.8
18.0
9.2
13.67
0.114
DMF
b)
9.3
18.2
8.9
13.38
0.116
DMF
b)
9.5
17.5
8.0
13.01
0.114
Pyridine
a)
7.7
13.7
6.0
10.12
0.113
Pyridine
a)
8.0
13.8
5.8
10.52
0.116
Pyridine
a)
7.7
14.3
6.6
10.32
0.114
Pyridine
b)
9.0
16.8
7.8
13.68
0.110
Pyridine
b)
8.7
16.7
8.0
13.03
0.111
Pyridine
b)
8.7
16.8
8.1
13.17
0.113
Acetonitrile
a)
6.9
13.6
6.7
9.47
0.107
Diaphragm clogged
Acetonitrile
a)
6.1
13.8
7.7
8.95
0.104
after titration
Acetonitrile
a)
6.2
13.8
7.6
9.63
0.107
Acetonitrile
b)
5.8
16.3
10.5
12.36
0.104
Diaphragm clogged
after titration
Acetonitrile
b)
6.0
16.3
10.3
12.51
0.104
Acetonitrile
b)
6.2
16.0
9.8
11.98
0.104
Remarks
II. Phenol; titrant: KOH in IPA
Solvent
Electr.
pH init
pH end
d pH
pH EP
«TAN»
Ethanol
a)
7.8
11.7
3.9
-
-
Ethanol
a)
8.2
11.7
3.5
-
-
Ethanol
a)
7.9
11.6
3.7
-
-
Ethanol
b)
9.2
12.8
3.6
-
-
Ethanol
b)
8.9
12.7
3.8
-
-
Ethanol
b)
8.6
12.7
4.1
-
-
Isopropanol
a)
9.0
13.7
4.7
-
-
Isopropanol
a)
9.0
13.8
4.8
-
-
Isopropanol
a)
9.8
13.6
3.8
-
-
Isopropanol
b)
9.3
14.3
5.0
13.48
0.105
Isopropanol
b)
9.1
14.2
5.1
13.51
0.105
Isopropanol
b)
9.4
14.2
4.8
13.33
0.103
Tert. butanol
a)
8.7
14.0
5.3
-
-
Tert. butanol
a)
9.2
14.2
5.0
-
-
Tert. butanol
a)
10.8
14.2
3.4
-
-
Tert. butanol
b)
9.6
14.5
4.9
13.42
0.113
Tert. butanol
b)
10.1
14.5
4.4
13.55
0.114
Tert. butanol
b)
10.1
14.5
4.4
13.41
0.108
Acetone
a)
10.7
15.0
4.3
14.00
0.103
Acetone
a)
10.7
15.0
4.3
13.61
0.103
Acetone
a)
10.4
15.0
4.6
14.04
0.103
Non-aqueous titration of acids and bases with potentiometric endpoint indication
Remarks
19
Compilation of results: bases as titrants
Solvent
Electr.
pH init
pH end
d pH
pH EP
«TAN»
Acetone
b)
11.4
15.7
4.3
14.68
0.106
Remarks
Acetone
b)
11.8
15.6
3.8
14.43
0.106
Acetone
b)
12.1
15.6
3.5
14.52
0.107
MIBK
a)
6.6
13.3
6.7
-
-
MIBK
a)
6.8
12.8
6.0
-
-
MIBK
a)
7.6
13.0
5.4
-
-
MIBK
b)
8.2
14.4
6.2
-
-
MIBK
b)
8.6
14.6
6.0
-
-
MIBK
b)
9.2
14.0
4.8
-
-
DMF
a)
10.2
15.8
5.6
14.17
0.117
DMF
a)
11.4
15.4
4.0
13.32
0.120
DMF
a)
11.7
15.5
3.8
13.52
0.121
DMF
b)
11.3
17.4
6.1
15.78
0.115
DMF
b)
12.3
17.2
4.9
15.57
0.119
DMF
b)
12.1
17.2
5.1
15.59
0.115
Pyridine
a)
9.6
12.6
3.0
11.51
0.118
Pyridine
a)
9.7
13.2
3.5
11.87
0.120
Pyridine
a)
10.4
13.4
3.0
11.98
0.121
Pyridine
b)
9.4
16.0
6.6
14.85
0.116
Pyridine
b)
11.9
16.4
4.5
15.47
0.115
Pyridine
b)
11.4
16.3
4.9
15.29
0.117
Acetonitrile
a)
9.7
13.3
3.6
11.77
0.105
Diaphragm clogged
Acetonitrile
a)
10.3
13.4
3.1
11.88
0.105
after titration
Acetonitrile
a)
10.3
13.7
3.4
11.78
0.106
Acetonitrile
b)
10.5
15.9
5.4
14.65
0.104
Diaphragm clogged
Acetonitrile
b)
10.8
16.2
5.4
14.80
0.103
after titration
Acetonitrile
b)
10.7
16.2
5.5
14.73
0.103
III. Benzoic acid; titrant: TBAOH in IPA
Solvent
Electr.
pH init
pH end
d pH
pH EP
«TAN»
Ethanol
a)
3.9
11.1
7.2
8.50
0.103
Ethanol
a)
3.8
11.3
7.5
8.49
0.104
Ethanol
a)
3.8
11.2
7.4
8.34
0.103
Ethanol
b)
4.8
12.1
7.3
9.94
0.100
Ethanol
b)
4.6
12.6
8.0
9.51
0.104
Ethanol
b)
4.7
11.8
7.1
9.20
0.101
Isopropanol
a)
5.0
12.3
7.3
9.91
0.103
Isopropanol
a)
5.0
11.8
6.8
9.52
0.104
Isopropanol
a)
5.5
12.7
7.2
9.61
0.104
20
Remarks
Peter Bruttel
Compilation of results: bases as titrants
Solvent
Electr.
pH init
pH end
d pH
pH EP
«TAN»
Isopropanol
b)
5.5
14.0
8.5
11.08
0.104
Isopropanol
b)
5.8
14.2
8.4
11.30
0.104
Isopropanol
b)
5.5
14.0
8.5
10.98
0.104
Tert. butanol
a)
5.9
15.3
9.4
11.10
0.105
Tert. butanol
a)
5.7
15.3
9.6
10.88
0.100
Tert. butanol
a)
5.8
15.3
9.5
11.67
0.108
Tert. butanol
b)
7.3
15.9
8.6
12.05
0.104
Tert. butanol
b)
6.8
15.8
9.0
12.82
0.107
Tert. butanol
b)
6.7
15.7
9.0
11.87
0.104
Acetone
a)
7.5
13.0
5.5
11.33
0.103
Acetone
a)
6.8
13.5
6.7
11.27
0.103
Acetone
a)
6.4
13.4
7.0
10.97
0.102
Acetone
b)
8.2
15.4
7.2
12.91
0.103
Acetone
b)
8.0
15.8
7.8
13.13
0.103
Acetone
b)
7.5
15.2
7.7
12.53
0.103
MIBK
a)
4.4
11.7
7.3
9.09
0.108
MIBK
a)
4.0
11.7
7.7
8.72
0.109
MIBK
a)
4.1
11.8
7.7
8.75
0.104
MIBK
b)
5.7
12.5
6.8
9.55
0.108
MIBK
b)
5.6
12.6
7.0
10.04
0.111
MIBK
b)
5.5
12.6
7.1
9.59
0.108
DMF
a)
8.3
14.1
5.8
10.77
0.108
DMF
a)
8.4
14.0
5.6
11.18
0.114
DMF
a)
8.3
14.2
5.9
11.01
0.112
DMF
b)
9.3
15.7
6.4
12.53
0.108
DMF
b)
8.9
15.7
6.8
12.82
0.111
DMF
b)
9.3
15.7
6.4
12.49
0.112
Pyridine
a)
7.6
13.6
6.0
11.48
0.110
Pyridine
a)
7.7
13.7
6.0
11.53
0.110
Pyridine
a)
7.6
14.0
6.4
11.73
0.113
Pyridine
b)
9.1
16.0
6.9
13.90
0.115
Pyridine
b)
9.0
16.0
7.0
13.80
0.111
Pyridine
b)
8.7
15.7
7.0
13.11
0.109
Acetonitrile
a)
6.2
12.8
6.6
10.35
0.104
Diaphragm clogged
Acetonitrile
a)
6.7
13.0
6.3
10.16
0.104
after titration
Acetonitrile
a)
5.8
13.0
7.2
10.64
0.103
Acetonitrile
b)
4.0
11.6
7.6
10.04
0.103
Diaphragm clogged
Acetonitrile
b)
6.0
13.3
7.3
11.22
0.102
after titration
Acetonitrile
b)
6.3
14.4
8.1
11.78
0.103
Non-aqueous titration of acids and bases with potentiometric endpoint indication
Remarks
21
Compilation of results: bases as titrants
IV. Phenol; titrant: TBAOH in IPA
Solvent
Electr.
pH init
pH end
d pH
pH EP
«TAN»
Ethanol
a)
7.8
11.1
3.3
-
-
Ethanol
a)
7.8
11.2
3.4
-
-
Ethanol
a)
7.9
11.2
3.3
-
-
Ethanol
b)
8.6
12.2
3.6
-
-
Ethanol
b)
9.3
12.3
3.0
-
-
Ethanol
b)
8.9
12.3
3.4
-
-
Isopropanol
a)
8.7
12.3
3.6
11.93
0.106
Isopropanol
a)
8.7
12.3
3.6
11.88
0.104
Isopropanol
a)
7.5
11.6
4.1
11.26
0.101
Isopropanol
b)
9.3
14.0
4.7
13.59
0.112
Isopropanol
b)
9.5
13.8
4.3
13.31
0.105
Isopropanol
b)
8.4
14.2
5.8
13.50
0.105
Tert. butanol
a)
9.6
13.3
3.7
12.68
0.104
Tert. butanol
a)
8.8
13.9
5.1
13.26
0.106
Tert. butanol
a)
7.4
11.6
4.2
11.18
0.107
Tert. butanol
b)
9.6
15.7
6.1
14.71
0.103
Tert. butanol
b)
8.5
16.2
7.7
15.15
0.101
Tert. butanol
b)
9.5
16.1
6.6
15.26
0.105
Acetone
a)
9.6
13.0
3.4
12.07
0.104
Acetone
a)
11.2
13.8
2.6
13.17
0.105
Acetone
a)
10.1
14.0
3.9
13.33
0.104
Acetone
b)
11.2
15.2
4.0
14.64
0.102
Acetone
b)
11.3
15.1
3.8
14.58
0.101
Acetone
b)
11.6
15.5
3.9
14.87
0.104
MIBK
a)
5.0
11.5
6.5
-
-
MIBK
a)
6.2
11.7
5.5
-
-
MIBK
a)
5.6
11.6
6.0
-
-
MIBK
b)
6.8
12.5
5.7
-
-
MIBK
b)
7.5
12.5
5.0
-
-
MIBK
b)
6.5
12.6
6.1
-
-
DMF
a)
10.6
14.8
4.2
13.65
0.115
DMF
a)
10.6
13.8
3.2
12.94
0.116
DMF
a)
10.5
14.2
3.7
13.27
0.113
DMF
b)
11.5
16.0
4.5
14.71
0.112
DMF
b)
11.3
15.7
4.4
14.63
0.114
DMF
b)
11.8
15.9
4.1
14.68
0.116
22
Remarks
Peter Bruttel
Compilation of results: bases as titrants
Solvent
Electr.
pH init
pH end
d pH
pH EP
«TAN»
Pyridine
a)
9.7
14.1
4.4
13.14
0.113
Remarks
Pyridine
a)
9.6
14.2
4.6
13.22
0.116
Pyridine
a)
10.0
14.2
4.2
13.18
0.117
Pyridine
b)
9.7
14.8
5.1
14.20
0.120
Pyridine
b)
11.2
16.0
4.8
14.94
0.114
Pyridine
b)
11.2
15.8
4.6
14.91
0.114
Acetonitrile
a)
8.5
12.7
4.2
11.54
0.104
Diaphragm clogged
after titration
Acetonitrile
a)
9.3
13.1
3.8
11.96
0.106
Acetonitrile
a)
9.4
13.3
3.9
12.29
0.107
Acetonitrile
b)
10.0
14.2
4.2
13.28
0.104
Diaphragm clogged
Acetonitrile
b)
10.3
14.3
4.0
13.46
0.105
after titration
Acetonitrile
b)
10.4
14.4
4.0
13.47
0.103
Non-aqueous titration of acids and bases with potentiometric endpoint indication
23
Standard deviations of the electrode signals
Standard deviations of the electrode signals
Electrode
s pH init
s pH end
s d pH
LiCl sat. in ethanol (KOH)
0.309
0.181
0.349
s pH EP
0.149
TEA-Br in ethylene glycol (KOH)
0.333
0.178
0.332
0.186
LiCl sat. in ethanol (TBAOH)
0.297
0.227
0.281
0.160
TEA-Br in ethylene glycol (TBAOH)
0.323
0.217
0.258
0.218
LiCl sat. in ethanol
0.303
0.204
0.315
0.155
TEA-Br in ethylene glycol
0.328
0.197
0.295
0.202
Electrode
Mean of d pH
LiCl sat. in ethanol (KOH)
6.1
TEA-Br in ethylene glycol (KOH)
6.6
LiCl sat. in ethanol (TBAOH)
5.6
TEA-Br in ethylene glycol (TBAO
6.1
LiCl sat. in ethanol
5.8
TEA-Br in ethylene glycol
6.4
24
Peter Bruttel
Titration curves obtained with the Solvotrode (LiCl sat. in ethanol)
Titration curves obtained with the Solvotrode (LiCl sat. in ethanol)
Non-aqueous titration of acids and bases with potentiometric endpoint indication
25
Titration curves obtained with the Solvotrode (LiCl sat. in ethanol)
26
Peter Bruttel
Titration curves obtained with the Solvotrode (LiCl sat. in ethanol)
Non-aqueous titration of acids and bases with potentiometric endpoint indication
27
Titration curves obtained with the Solvotrode (LiCl sat. in ethanol)
28
Peter Bruttel
Titration curves obtained with the Solvotrode (LiCl sat. in ethanol)
Non-aqueous titration of acids and bases with potentiometric endpoint indication
29
Titration curves obtained with the Solvotrode (LiCl sat. in ethanol)
30
Peter Bruttel
Titration curves obtained with the Solvotrode (0.4 mol/L TEA-Br in ethylene glycol)
Titration curves obtained with the Solvotrode (0.4 mol/L TEA-Br in
ethylene glycol)
Non-aqueous titration of acids and bases with potentiometric endpoint indication
31
Titration curves obtained with the Solvotrode (0.4 mol/L TEA-Br in ethylene glycol)
32
Peter Bruttel
Titration curves obtained with the Solvotrode (0.4 mol/L TEA-Br in ethylene glycol)
Non-aqueous titration of acids and bases with potentiometric endpoint indication
33
Titration curves obtained with the Solvotrode (0.4 mol/L TEA-Br in ethylene glycol)
34
Peter Bruttel
Titration curves obtained with the Solvotrode (0.4 mol/L TEA-Br in ethylene glycol)
Non-aqueous titration of acids and bases with potentiometric endpoint indication
35
Titration curves obtained with the Solvotrode (0.4 mol/L TEA-Br in ethylene glycol)
36
Peter Bruttel
Compilation of results: acids as titrants
Compilation of results: acids as titrants
a) Electrode with LiCl sat. in ethanol
b) Electrode with TEA-Br in ethylene glycol
I. Ethanolamine; titrant: perchloric acid in glacial acetic acid (HAc)
Solvent
Electr.
pH init
pH end
d pH
pH EP
«TAN»
Ethanol
a)
6.7
-1.9
8.6
0.56
0.100
Ethanol
a)
6.8
-1.8
8.6
0.40
0.100
Ethanol
a)
7.1
-1.7
8.8
0.65
0.100
Ethanol
b)
7.3
-1.0
8.3
1.40
0.101
Ethanol
b)
7.6
-1.0
8.6
1.03
0.099
Ethanol
b)
8.1
-1.0
9.1
1.30
0.100
Acetone
a)
6.4
-5.4
11.8
-1.75
0.098
Acetone
a)
6.5
-5.5
12.0
-0.90
0.096
Acetone
a)
6.4
-5.5
11.9
-2.31
0.099
Acetone
b)
7.6
-4.2
11.8
-1.12
0.099
Acetone
b)
7.5
-4.2
11.7
-1.02
0.100
Acetone
b)
7.7
-4.2
11.9
-0.30
0.098
Acetonitrile
a)
7.8
-5.2
13.0
-1.86
0.100
Acetonitrile
a)
7.7
-5.4
13.1
-0.79
0.100
Acetonitrile
a)
7.8
-5.3
13.1
-2.08
0.099
Acetonitrile
b)
8.4
-4.6
13.0
-1.03
0.098
Acetonitrile
b)
8.4
-4.3
12.7
-1.29
0.100
Acetonitrile
b)
8.5
-4.4
12.9
-1.51
0.099
Dioxane/IPA 1:1
a)
5.8
-3.2
9.0
-0.17
0.102
Dioxane/IPA 1:1
a)
5.8
-3.3
9.1
-0.53
0.102
Dioxane/IPA 1:1
a)
6.0
-3.3
9.3
-0.58
0.102
Dioxane/IPA 1:1
b)
6.8
-2.4
9.2
0.31
0.100
Dioxane/IPA 1:1
b)
6.7
-2.3
9.0
0.30
0.099
Dioxane/IPA 1:1
b)
6.7
-2.2
8.9
1.01
0.100
MIBK/HAc/toluene 1:1:1
a)
0.7
-5.7
6.4
-3.11
0.100
MIBK/HAc/toluene 1:1:1
a)
0.7
-5.7
6.4
-2.66
0.101
MIBK/HAc/toluene 1:1:1
a)
0.7
-5.7
6.4
-3.31
0.100
MIBK/HAc/toluene 1:1:1
b)
0.7
-5.2
5.9
-2.98
0.099
MIBK/HAc/toluene 1:1:1
b)
1.0
-5.0
6.0
-2.66
0.099
MIBK/HAc/toluene 1:1:1
b)
1.1
-4.8
5.9
-2.49
0.100
Toluene/IPA/water 500:495:5
a)
6.7
-2.9
9.6
-0.58
0.099
Toluene/IPA/water 500:495:5
a)
6.5
-2.7
9.2
-0.40
0.099
Toluene/IPA/water 500:495:5
a)
6.4
-2.3
8.7
0.38
0.100
Non-aqueous titration of acids and bases with potentiometric endpoint indication
37
Compilation of results: acids as titrants
Solvent
Electr.
pH init
pH end
d pH
pH EP
«TAN»
Toluene/IPA/water 500:495:5
b)
7.4
-1.2
8.6
1.02
0.100
Toluene/IPA/water 500:495:5
b)
7.6
-1.2
8.8
0.92
0.098
Toluene/IPA/water 500:495:5
b)
7.3
-1.4
8.7
0.77
0.100
II. Aniline; titrant: perchloric acid in glacial acetic acid (HAc)
Solvent
Electr.
pH init
pH end
d pH
pH EP
«TAN»
Ethanol
a)
4.2
-1.6
5.8
-0.01
0.100
Ethanol
a)
4.2
-1.6
5.8
-0.06
0.100
Ethanol
a)
4.2
-1.6
5.8
-0.08
0.100
Ethanol
b)
4.7
-0.8
5.5
0.57
0.101
Ethanol
b)
5.1
-0.9
6.0
0.60
0.101
Ethanol
b)
4.8
-0.9
5.7
0.61
0.100
Acetone
a)
1.8
-5.2
7.0
-2.83
0.099
Acetone
a)
1.8
-5.2
7.0
-2.84
0.099
Acetone
a)
1.8
-5.3
7.1
-2.86
0.100
Acetone
b)
3.0
-4.0
7.0
-1.47
0.100
Acetone
b)
2.9
-4.1
7.0
-1.49
0.100
Acetone
b)
3.0
-4.1
7.1
-1.73
0.100
Acetonitrile
a)
2.5
-5.0
7.5
-2.56
0.101
Acetonitrile
a)
2.5
-5.1
7.6
-2.71
0.100
Acetonitrile
a)
2.5
-4.9
7.4
-2.56
0.100
Acetonitrile
b)
3.0
-4.4
7.4
-1.97
0.101
Acetonitrile
b)
3.0
-4.4
7.4
-1.93
0.101
Acetonitrile
b)
3.0
-4.5
7.5
-2.05
0.100
Dioxane/IPA 1:1
a)
1.8
-3.4
5.2
-1.78
0.097
Dioxane/IPA 1:1
a)
2.0
-3.3
5.3
-1.76
0.097
Dioxane/IPA 1:1
a)
2.0
-3.2
5.2
-1.75
0.098
Dioxane/IPA 1:1
b)
3.0
-2.2
5.2
-0.66
0.098
Dioxane/IPA 1:1
b)
3.0
-2.3
5.3
-0.72
0.098
Dioxane/IPA 1:1
b)
3.0
-2.2
5.2
-0.71
0.097
MIBK/HAc/toluene 1:1:1
a)
0.3
-5.6
5.9
-3.15
0.100
MIBK/HAc/toluene 1:1:1
a)
0.3
-5.6
5.9
-3.01
0.101
MIBK/HAc/toluene 1:1:1
a)
0.2
-5.5
5.7
-3.22
0.100
MIBK/HAc/toluene 1:1:1
b)
0.7
-5.1
5.8
-2.53
0.100
MIBK/HAc/toluene 1:1:1
b)
0.7
-4.9
5.6
-2.48
0.100
MIBK/HAc/toluene 1:1:1
b)
0.7
-4.9
5.6
-2.41
0.101
38
Peter Bruttel
Compilation of results: acids as titrants
Solvent
Electr.
pH init
pH end
d pH
pH EP
«TAN»
Toluene/IPA/water 500:495:5
a)
3.0
-2.6
5.6
-1.07
0.101
Toluene/IPA/water 500:495:5
a)
3.2
-2.6
5.8
-1.05
0.101
Toluene/IPA/water 500:495:5
a)
3.1
-2.4
5.5
-1.03
0.101
Toluene/IPA/water 500:495:5
b)
4.1
-1.2
5.3
0.07
0.101
Toluene/IPA/water 500:495:5
b)
3.8
-1.5
5.3
-0.02
0.101
Toluene/IPA/water 500:495:5
b)
4.0
-1.2
5.2
-0.07
0.101
III. Urea; titrant: perchloric acid in glacial acetic acid (HAc)
Solvent
Electr.
pH init
pH end
d pH
pH EP
«TAN»
Ethanol
a)
-
-
-
-
-
Ethanol
a)
-
-
-
-
-
Ethanol
a)
-
-
-
-
-
Ethanol
b)
-
-
-
-
-
Ethanol
b)
-
-
-
-
-
Ethanol
b)
-
-
-
-
-
Acetone
a)
-
-
-
-
-
Acetone
a)
-
-
-
-
-
Acetone
a)
-
-
-
-
-
Acetone
b)
-
-
-
-
-
Acetone
b)
-
-
-
-
-
Acetone
b)
-
-
-
-
-
Acetonitrile
a)
-
-
-
-
-
Acetonitrile
a)
-
-
-
-
-
Acetonitrile
a)
-
-
-
-
-
Acetonitrile
b)
-
-
-
-
-
Acetonitrile
b)
-
-
-
-
-
Acetonitrile
b)
-
-
-
-
-
Dioxane/IPA 1:1
a)
-
-
-
-
-
Dioxane/IPA 1:1
a)
-
-
-
-
-
Dioxane/IPA 1:1
a)
-
-
-
-
-
Dioxane/IPA 1:1
b)
-
-
-
-
-
Dioxane/IPA 1:1
b)
-
-
-
-
-
Dioxane/IPA 1:1
b)
-
-
-
-
-
MIBK/HAc/toluene 1:1:1
a)
-
-
-
-
-
MIBK/HAc/toluene 1:1:1
a)
-
-
-
-
-
MIBK/HAc/toluene 1:1:1
a)
-
-
-
-
-
Non-aqueous titration of acids and bases with potentiometric endpoint indication
39
Compilation of results: acids as titrants
Solvent
Electr.
pH init
pH end
d pH
pH EP
«TAN»
MIBK/HAc/toluene 1:1:1
b)
-
-
-
-
-
MIBK/HAc/toluene 1:1:1
b)
-
-
-
-
-
MIBK/HAc/toluene 1:1:1
b)
-
-
-
-
-
Toluene/IPA/water 500:495:5
a)
-
-
-
-
-
Toluene/IPA/water 500:495:5
a)
-
-
-
-
-
Toluene/IPA/water 500:495:5
a)
-
-
-
-
-
Toluene/IPA/water 500:495:5
b)
-
-
-
-
-
Toluene/IPA/water 500:495:5
b)
-
-
-
-
-
Toluene/IPA/water 500:495:5
b)
-
-
-
-
-
IV. Ethanolamine; titrant: HCl in IPA
Solvent
Electr.
pH init
pH end
d pH
pH EP
«TAN»
Ethanol
a)
8.5
-1.1
9.6
1.99
0.102
Ethanol
a)
8.4
-1.3
9.7
2.28
0.104
Ethanol
a)
8.4
-1.3
9.7
1.83
0.103
Ethanol
b)
8.7
-0.4
9.1
2.83
0.102
Ethanol
b)
8.8
-0.4
9.2
2.91
0.101
Ethanol
b)
8.8
-0.5
9.3
2.85
0.101
Acetone
a)
8.1
-2.0
10.1
2.13
0.100
Acetone
a)
8.4
-1.8
10.2
2.10
0.100
Acetone
a)
8.3
-1.8
10.1
2.40
0.099
Acetone
b)
9.4
-1.1
10.5
2.92
0.100
Acetone
b)
9.3
-1.1
10.4
3.05
0.099
Acetone
b)
9.2
-1.2
10.4
3.12
0.099
Acetonitrile
a)
8.7
-2.0
10.7
1.72
0.102
Acetonitrile
a)
8.7
-2.0
10.7
2.10
0.101
Acetonitrile
a)
8.8
-2.0
10.8
1.96
0.101
Acetonitrile
b)
9.0
-1.8
10.8
3.02
0.100
Acetonitrile
b)
9.0
-1.8
10.8
2.98
0.100
Acetonitrile
b)
9.1
-1.8
10.9
2.17
0.101
Dioxane/IPA 1:1
a)
6.4
-1.5
7.9
1.94
0.099
Dioxane/IPA 1:1
a)
6.1
-1.6
7.7
1.95
0.099
Dioxane/IPA 1:1
a)
6.3
-1.6
7.9
1.59
0.100
Dioxane/IPA 1:1
b)
7.0
-0.8
7.8
3.00
0.098
Dioxane/IPA 1:1
b)
7.1
-0.7
7.8
3.00
0.098
Dioxane/IPA 1:1
b)
7.2
-0.8
8.0
2.94
0.098
40
Peter Bruttel
Compilation of results: acids as titrants
Solvent
Electr.
pH init
pH end
d pH
pH EP
«TAN»
MIBK/HAc/toluene 1:1:1
a)
0.6
-3.7
4.3
-1.47
0.099
MIBK/HAc/toluene 1:1:1
a)
0.6
-3.6
4.2
-1.40
0.099
MIBK/HAc/toluene 1:1:1
a)
0.7
-3.7
4.4
-1.35
0.099
MIBK/HAc/toluene 1:1:1
b)
1.0
-3.4
4.4
1.04
0.098
MIBK/HAc/toluene 1:1:1
b)
1.1
-3.3
4.4
-0.94
0.098
MIBK/HAc/toluene 1:1:1
b)
1.0
-3.3
4.3
-1.03
0.098
Toluene/IPA/water 500:495:5
a)
6.9
-0.5
7.4
2.33
0.101
Toluene/IPA/water 500:495:5
a)
6.6
-0.5
7.1
2.88
0.099
Toluene/IPA/water 500:495:5
a)
7.9
-0.5
8.4
2.84
0.100
Toluene/IPA/water 500:495:5
b)
7.6
0.2
7.4
3.55
0.099
Toluene/IPA/water 500:495:5
b)
8.3
0.2
8.1
3.83
0.099
Toluene/IPA/water 500:495:5
b)
8.6
0.2
8.4
4.29
0.098
Solvent
Electr.
pH init
pH end
d pH
pH EP
«TAN»
Ethanol
a)
4.1
-1.4
5.5
0.30
0.100
Ethanol
a)
4.4
-1.2
5.6
0.32
0.099
Ethanol
a)
4.2
-1.3
5.5
0.28
0.100
Ethanol
b)
4.6
-0.5
5.1
0.91
0.099
Ethanol
b)
4.8
-0.5
5.3
0.87
0.100
Ethanol
b)
4.5
-0.5
5.0
0.92
0.099
Acetone
a)
2.2
-2.1
4.3
-0.50
0.100
Acetone
a)
2.2
-2.0
4.2
-0.38
0.099
Acetone
a)
2.4
-2.0
4.4
-0.41
0.100
Acetone
b)
3.0
-1.2
4.2
0.40
0.099
Acetone
b)
2.8
-1.6
4.4
0.48
0.099
Acetone
b)
3.2
-1.3
4.5
0.31
0.100
Acetonitrile
a)
2.4
-2.5
4.9
-0.91
0.100
Acetonitrile
a)
2.5
-2.4
4.9
-0.98
0.100
Acetonitrile
a)
1.8
-2.7
4.5
-1.19
0.099
Acetonitrile
b)
2.6
-2.1
4.7
-0.63
0.100
Acetonitrile
b)
2.6
-2.0
4.6
-0.59
0.100
Acetonitrile
b)
2.5
-2.0
4.5
-0.60
0.100
Dioxane/IPA 1:1
a)
2.2
-1.6
3.8
-0.44
0.099
Dioxane/IPA 1:1
a)
2.3
-1.6
3.9
-0.47
0.100
Dioxane/IPA 1:1
a)
2.2
-1.6
3.8
-0.44
0.099
V. Aniline; titrant: HCl in IPA
Non-aqueous titration of acids and bases with potentiometric endpoint indication
41
Compilation of results: acids as titrants
Solvent
Electr.
pH init
pH end
d pH
pH EP
«TAN»
Dioxane/IPA 1:1
b)
3.0
-0.8
3.8
0.40
0.099
Dioxane/IPA 1:1
b)
3.2
-0.8
4.0
0.36
0.099
Dioxane/IPA 1:1
b)
3.0
-0.8
3.8
0.32
0.099
MIBK/HAc/toluene 1:1:1
a)
0.5
-3.5
4.0
-1.84
0.100
MIBK/HAc/toluene 1:1:1
a)
0.4
-3.6
4.0
-1.83
0.100
MIBK/HAc/toluene 1:1:1
a)
0.5
-3.5
4.0
-1.77
0.100
MIBK/HAc/toluene 1:1:1
b)
0.9
-3.2
4.1
-1.41
0.099
MIBK/HAc/toluene 1:1:1
b)
0.8
-3.2
4.0
-1.39
0.099
MIBK/HAc/toluene 1:1:1
b)
0.8
-3.2
4.0
-1.47
0.100
Toluene/IPA/water 500:495:5
a)
3.3
-0.5
3.8
0.46
0.099
Toluene/IPA/water 500:495:5
a)
3.1
-0.5
3.6
0.43
0.099
Toluene/IPA/water 500:495:5
a)
3.0
-0.4
3.4
0.46
0.099
Toluene/IPA/water 500:495:5
b)
3.7
-0.1
3.8
1.08
0.098
Toluene/IPA/water 500:495:5
b)
3.5
-0.4
3.9
1.06
0.098
Toluene/IPA/water 500:495:5
b)
3.5
-0.1
3.6
1.04
0.098
Solvent
Electr.
pH init
pH end
d pH
pH EP
«TAN»
Ethanol
a)
-
-
-
-
-
Ethanol
a)
-
-
-
-
-
Ethanol
a)
-
-
-
-
-
Ethanol
b)
-
-
-
-
-
Ethanol
b)
-
-
-
-
-
Ethanol
b)
-
-
-
-
-
Acetone
a)
-
-
-
-
-
Acetone
a)
-
-
-
-
-
Acetone
a)
-
-
-
-
-
Acetone
b)
-
-
-
-
-
Acetone
b)
-
-
-
-
-
Acetone
b)
-
-
-
-
-
Acetonitrile
a)
-
-
-
-
-
Acetonitrile
a)
-
-
-
-
-
Acetonitrile
a)
-
-
-
-
-
Acetonitrile
b)
-
-
-
-
-
Acetonitrile
b)
-
-
-
-
-
Acetonitrile
b)
-
-
-
-
-
VI. Urea; titrant: HCl in IPA
42
Peter Bruttel
Compilation of results: acids as titrants
Solvent
Electr.
pH init
pH end
d pH
pH EP
«TAN»
Dioxane/IPA 1:1
a)
-
-
-
-
-
Dioxane/IPA 1:1
a)
-
-
-
-
-
Dioxane/IPA 1:1
a)
-
-
-
-
-
Dioxane/IPA 1:1
b)
-
-
-
-
-
Dioxane/IPA 1:1
b)
-
-
-
-
-
Dioxane/IPA 1:1
b)
-
-
-
-
-
MIBK/HAc/toluene 1:1:1
a)
-
-
-
-
-
MIBK/HAc/toluene 1:1:1
a)
-
-
-
-
-
MIBK/HAc/toluene 1:1:1
a)
-
-
-
-
-
MIBK/HAc/toluene 1:1:1
b)
-
-
-
-
-
MIBK/HAc/toluene 1:1:1
b)
-
-
-
-
-
MIBK/HAc/toluene 1:1:1
b)
-
-
-
-
-
Toluene/IPA/water 500:495:5
a)
-
-
-
-
-
Toluene/IPA/water 500:495:5
a)
-
-
-
-
-
Toluene/IPA/water 500:495:5
a)
-
-
-
-
-
Toluene/IPA/water 500:495:5
b)
-
-
-
-
-
Toluene/IPA/water 500:495:5
b)
-
-
-
-
-
Toluene/IPA/water 500:495:5
b)
-
-
-
-
-
Non-aqueous titration of acids and bases with potentiometric endpoint indication
43
Standard deviations of the electrode signals
Standard deviations of the electrode signals
Electrode
s pH init
s pH end
s d pH
s pH EP
LiCl sat. in ethanol (perchloric acid)
0.059
0.072
0.093
0.196
TEA-Br in ethylene glycol (perchloric acid)
0.095
0.074
0.107
0.140
LiCl sat. in ethanol (HCl)
0.141
0.053
0.117
0.099
TEA-Br in ethylene glycol (HCl)
0.108
0.046
0.111
0.166
LiCl sat. in ethanol
0.100
0.062
0.105
0.147
TEA-Br in ethylene glycol
0.102
0.060
0.109
0.153
Electrode
Mean of d pH
LiCl sat. in ethanol (perchloric acid)
7.9
TEA-Br in ethylene glycol (perchloric acid)
7.8
LiCl sat. in ethanol (HCl)
6.4
TEA-Br in ethylene glycol (HCl)
6.4
LiCl sat. in ethanol
7.2
TEA-Br in ethylene glycol
7.1
44
Peter Bruttel
Titration curves obtained with the Solvotrode (LiCl sat. in ethanol)
Titration curves obtained with the Solvotrode (LiCl sat. in ethanol)
Non-aqueous titration of acids and bases with potentiometric endpoint indication
45
Titration curves obtained with the Solvotrode (LiCl sat. in ethanol)
46
Peter Bruttel
Titration curves obtained with the Solvotrode (LiCl sat. in ethanol)
Non-aqueous titration of acids and bases with potentiometric endpoint indication
47
Titration curves obtained with the Solvotrode (LiCl sat. in ethanol)
48
Peter Bruttel
Titration curves obtained with the Solvotrode (LiCl sat. in ethanol)
Titration curves obtained with the Solvotrode (0.4 mol/L TEA-Br in ethylene glycol)
Titration curves obtained with the Solvotrode (0.4 mol/L TEA-Br in
ethylene glycol)
Non-aqueous titration of acids and bases with potentiometric endpoint indication
49
Titration curves obtained with the Solvotrode (0.4 mol/L TEA-Br in ethylene glycol)
50
Peter Bruttel
Titration curves obtained with the Solvotrode (0.4 mol/L TEA-Br in ethylene glycol)
Non-aqueous titration of acids and bases with potentiometric endpoint indication
51
Titration curves obtained with the Solvotrode (0.4 mol/L TEA-Br in ethylene glycol)
52
Peter Bruttel
Titration curves obtained with the Solvotrode (0.4 mol/L TEA-Br in ethylene glycol)
Non-aqueous titration of acids and bases with potentiometric endpoint indication
53
Titration curves obtained with the Solvotrode (LiCl sat. in ethanol)
Titration curves obtained with the Solvotrode (LiCl sat. in ethanol)
54
Peter Bruttel
Titration curves obtained with the Solvotrode (LiCl sat. in ethanol)
Titration curves obtained with the Solvotrode (0.4 mol/L TEA-Br in ethylene glycol)
Titration curves obtained with the Solvotrode (0.4 mol/L TEA-Br in
ethylene glycol)
Non-aqueous titration of acids and bases with potentiometric endpoint indication
55
Titration curves obtained with the Solvotrode (0.4 mol/L TEA-Br in ethylene glycol)
56
Peter Bruttel