Thermodynamic studies of aqueous solutions of ammonium based nitrate protic ionic liquids at different temperatures (288.15?K to 303.15?K)and 101.325?kPa: A volumetric approach

Article abstract of DOI:10.1016/j.molliq.2019.110884

We report the synthesis of two protic ionic liquids (PILs)through atom–economic neutralization reaction between alkylamine (diethlyamine (DEA)and triethylamine (TEA))and nitric acid. The product ionic liquids are characterized by ¹H NMR spectra. The density property of aqueous solutions of synthesized PILs, namely, diethylammonium nitrate (DEAN)and triethylammonium nitrate (TEAN)were measured in the concentration range of ~0.01 ? ~0.5 mol·kg^?1for the temperature range of 288.15 K to 303.15 K and at 101.325 kPa. The measured densities were used to calculate the apparent molar volume (V_?), partial molar volume of solvent (Vˉ₁)and solute (Vˉ₂)at all studied temperatures. The limiting apparent molar volumes (V_? ⁰)are reported. The apparent molar expansivity (E_?)of PILs at finite concentrations as well as at infinite dilutions are reported at 293.15 and 298.15 K. It is observed that water structure making effect exhibited by cations is governed by the hydration of the cations, while the overall kosmotropic effect depends upon the basicity and shape factor of the cation concerned. The hydrophobic solute–solute interactions and ion–pair formation may be influencing the deviation parameter (B_V)of Debye-Hückel equation for volumes. These results are discussed.

Full text of DOI:10.1016/j.molliq.2019.110884

Accepted Manuscript
Thermodynamic studies of aqueous solutions of ammonium based
nitrate protic ionic liquids at different temperatures (288.15K to
303.15K) and 101.325kPa: A volumetric approach
Kunal R. Patil, Vasim R. Shaikh, Sarika B. Borse, Dilip H.
Dagade, Kesharsingh J. Patil
PII:
DOI:
Article Number:
Reference:
S0167-7322(19)31341-8
https://doi.org/10.1016/j.molliq.2019.110884
110884
MOLLIQ 110884
To appear in:
Journal of Molecular Liquids
Received date:
Revised date:
Accepted date:
7 March 2019
18 April 2019
30 April 2019
Please cite this article as: K.R. Patil, V.R. Shaikh, S.B. Borse, et al., Thermodynamic
studies of aqueous solutions of ammonium based nitrate protic ionic liquids at different
temperatures (288.15K to 303.15K) and 101.325kPa: A volumetric approach, Journal of
Molecular Liquids, https://doi.org/10.1016/j.molliq.2019.110884
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ACCEPTED MANUSCRIPT
Thermodynamic Studies of Aqueous Solutions of Ammonium Based
Nitrate Protic Ionic Liquids at Different Temperatures (288.15 K to
303.15 K) and 101.325 kPa: A Volumetric Approach
Kunal R. Patil,a,b Vasim R. Shaikh,c Sarika B. Borse,c Dilip H. Dagadea and Kesharsingh
J. Patil*,c
aDepartment of Chemistry, Shivaji University, Kolhapur–416004, India
bKCES’s Post Graduate College of Sciences, Technology and Research, M. J. College Campus,
Jalgaon–425002, India
cSchool of Chemical Sciences, Kavayitri Bahinabai Chaudhari North Maharashtra University,
Jalgaon–425001, India
Abstract: We report the synthesis of two protic ionic liquids (PILs) through atom–economic
neutralization reaction between alkylamine (diethlyamine (DEA) and triethylamine (TEA)) and
nitric acid. The product ionic liquids are characterized by 1H NMR spectra. The density property
of aqueous solutions of synthesised PILs, namely, diethylammonium nitrate (DEAN) and
triethylammonium nitrate (TEAN) were measured in the concentration range of ~0.01−~0.5
mol·kg−1for the temperature range of 288.15 K to 303.15 K and at 101.325 kPa. The measured
V
densities were used to calculate the apparent molar volume (  ), partial molar volume of solvent
V 0
(
V 1 ) and solute (V 2 ) at all studied temperatures. The limiting apparent molar volumes ( ) are

E
reported. The apparent molar expansivity (  ) of PILs at finite concentrations as well as at
infinite dilutions are reported at 293.15 and 298.15 K. It is observed that water structure making
1

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effect exhibited by cations is governed by the hydration of the cations, while the overall
kosmotropic effect depends upon the basicity and shape factor of the cation concerned. The
hydrophobic solute–solute interactions and ion–pair formation may be influencing the deviation
parameter (BV) of DebyeHückel equation for volumes.These results are discussed.
*Corresponding Author: E–mail: patilkesharsingh@hotmail.com
Keywords: Protic ionic liquids, Partial molar volume, Isobaric expansivity, Kosmotropic effect.
1.
Introduction
Ionic liquids (ILs)are known as organic molten or fused salts that are liquid at low
temperatures generally below 373 K[1]. The recent literature is getting surged day by day the
reports of ILs as solvent, catalyst and variety of other uses as solubilization of polymers or their
use for degradation [1,2]. It is noted that in literature, the properties of ILs or mixtures of ILs
with various solvents including water are being reported over the whole concentration range
[3–5]. Such data may not yield useful information about ion–ion and ion–solvent interactions at
infinitely dilute solution. There is a need of good quality thermodynamic properties data in finite
as well as at infinite concentration of ILs especially in water as a solvent. There are few studies
which tried to probe for the molecular and ion interactions in dilute concentration range
employing volumetric, speed of sound, viscosity and vapor pressure osmometry measurements
[6–15].
The protic ionic liquid (PIL) is a well–characterized sub class of ILs which are simpler,
cheaper and environment friendly to synthesize designed from the transfer of proton from
Brønsted acid to Brønsted base with no by–product formation ( HA B 

BH 



A 
)

2

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[2,10,11]. The first ionic liquid discovered by Gabriel in 1888 was ethanolammonium nitrate,
having melting point of 325−328 K and was besides the first PIL [16]. Another ionic liquid
ethylammonium nitrate having melting point 285 K was synthesized and reported in the
scientific literature by Walden in 1914 [17], while Mirejovsky and Arnett [18] have reported the
synthesis of ethylammonium nitrate which is having all similar properties as that of water except
heat capacity. Among the substitutes to presently used solvents, significant attention has been
earned by the PILs because of their distinctive and tunable physical and chemical properties [2].
The PILs having distinguished properties such as low vapour pressure, basicity, thermal stability,
high ionicity, hydrophobicity, hydrogen bonding, polarity, large chemical window, non–
flammability, and so on [1,2,19,]. These properties of PILs can be tuned for desired application
by choosing different combinations of anions and cations and that’s the reason for describes
them as ‘designer solvent’ [20,21].
Alkylammonium nitrate PILs with the physiognomies of strong solubility, H–bond
formation ability, good catalytic and additives properties have invited extensive attention from
both academic community and industry [19–29]. Summers and Fowers [28] observed that, the
ethylammonium nitrate [EAN]PIL acts as a denatured-reducing agent used for the recovery of
reduced-denatured lysozyme which gives 75 % of its activity in the regular renaturation methods.
EAN also acts as the preventing agents of the aggregation of lysozyme i.e. acting as an osmolyte
[28]. The above observations are important to understand the denaturation of bio-polymer or
proteins in water [30,31].
Recently, in our laboratory we have synthesized and characterized the protic ionic liquids
(PILs) successfully [10,11].As a continuance of our PILs studies, we report in this
communication, the synthesis of two protic ionic liquids namely, diethylammonium nitrate
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[DEAN] and triethylammonium nitrate [TEAN] and studies related to their volumetric behaviour
in dilute aqueous solutions (~0.01 to ~0.5 mol·kg−1) for the temperature range of 288.15 to
303.15 K and at 101.325 kPa. Using experimental density data, the calculations of parameters
V
like apparent molar volume ( ), partial molar volume of solvent ( ) and solute ( ), isobaric
V 1 V 2

E
V 0

expansivity ( ) and apparent molar expansivity (  ), the limiting apparent molar volume (
)

and limiting apparent molar expansivity ( 0 ) were made. The results are presented and
E
discussed.
2.
Experimental procedure
2.1
Materials
All chemicals were purchased from different sources which were required for the
synthesis of ammonium based nitrate protic ionic liquids. These are listed in Table 1 with mass
fraction purity. All were used without further purification.
2.2
Synthesis of protic ionic liquids
Synthesis of PILs namely diethylammonium nitrate [DEAN] and triethylammonium
nitrate [TEAN] was carried out in same way using reported methods [22,23]. The DEAN and
TEAN are prepared by a simple acid–base reaction: stoichiometric quantity of nitric acid is
added into alkylamine (diethlyamine [DEA] and triethylamine [TEA]) respectively. The
diethylamine were charged into a three neck round bottom flask equipped with a Nitrogen gas
purging and a dropping funnel with the tip under stopcock. Then nitric acid was added drop wise
into diethlyamine using dropping funnel. The above mixture in the round bottom flask was kept
in an ice cold (273 K) condition with constant stirring as the reaction is highly exothermic. The
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reaction mixture was stirred at 273 K for 1 h and then at 303K for 4−5 h for completion of
reaction. Any traces of reactant was removed by applying high vacuum at 323 K and finally, to
obtain pale yellow solid product as DEAN. The same procedure was followed for the synthesis
of TEAN which yields white crystals. The melting point of synthesized DEAN and TEAN are
367 K and 385 K, respectively which agree well those reported in literature [22,23].
After drying at appropriate vacuum and temperature conditions, resulting PILs were then
stored in dry conditions under phosphorous pentaoxide (P2O5) in a desiccator. The structures and
purity of the DEAN and TEAN were confirmed by using 1H NMR spectra obtained at 300 MHz
Bruker instrument in CDCl3 as a solvent (Supplementary Data, Fig.S1−S2). No any residues of
1
impurities were detected in H NMR spectra. The chemical structures of synthesized PILs are
schematically represented in Fig. 1. Water contents in the synthesized PILs were determined by
Karl–Fischer titration and found to be 0.0025 mass fractions for DEAN and 0.0021 mass
fractions for TEAN respectively. These water contents were taken into consideration during
preparation of solutions to determine concentrations.
2.3
Preparations of sample solutions
All the solutions of studied PILs were prepared on molality basis at room temperature in
the air tight glass vessels and whenever necessary converted to molarity scale using density data.
Quartz doubly distilled water was used for the entire work. A SHIMADZU AUW220D balance
having readability of 0.01 mg was used for weighing. The standard uncertainties in the molality
of solutions were found to be ± 5·10−5mol·kg−1.
2.4
Density Measurements
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The density measurements were made using DMA5000 Anton Paar Digital
Densitometer at 288.15, 293.15, 298.15 and 303.15±0.01K. The densitometer was calibrated
using the air and water at the studied temperatures. After applying the humidity and lab pressure
corrections, the uncertainty in the density measurements was found to be ±3∙103 kg∙m3. The
methodology of density measurements and other details are described earlier [13,14,32]
3. Results
3.1
Density and Apparent Molar Volume
The experimental density ( ) data for aqueous solutions of DEAN (0.01923 to 0.50456

molkg1) and for aqueous solutions of TEAN (0.01991 molkg1 and 0.51256 molkg1) at
different temperatures (288.15, 293.15, 298.15 and 303.15 K) are collected in Table 2 and Table
3, respectively. The variations of data as a function of molality of DEAN and TEAN at all

studied temperatures are shown in Fig.S3 and Fig.S4 (Supplementary Data: Fig.S3 and Fig.S4),
respectively.
Further, the data were used to calculate the apparent molar volumes (V ) of both

studied PILs in aqueous solutions at finite concentration by using the Eq. (1) [33]
(0  ) M
V 

(1)

m0

where 0 and
are the densities( in kg∙m3) of solvent and solution, respectively, m is molality of

the solute (mol∙kg1) and M is the molar mass of the solute (kg∙mol1).
The V data of DEAN and TEAN in aqueous solutions along with their uncertainties at studied
temperatures are collected in Table 2 and Table 3, respectively.
The V data can also be expressed as [33–35],
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1
0

2
V V  SV c  BV c
(2)

where 0 is apparent molar volume of the solute at infinite dilution, SV is DebyeHückel limiting
V
law coefficient (1.697, 1.782, 1.868and 1.955∙106 (mol∙mm)3/2 for 1:1 electrolyte solutions at
288.15, 293.15, 298.15 and 303.15 K, respectively) [32,34,36], c is the concentration of the
solute in aqueous solutions (mol∙dm3) and BV is a deviation parameter (m6∙mol2).
V  SV c1/2
The variation of
as a function of concentration (c/mol∙dm3) of DEAN and

TEAN in aqueous solutions at 288.15, 293.15, 298.15 and 303.15 K are shown in Fig. 2 and Fig.
3, respectively. The limiting apparent molar volume ( 0 ) are obtained by the smooth
V
extrapolation of parameter (
1/2 )to infinitely dilute solutions and the value of BV
V  SV c

0
V
parameters are estimated from the slope of the graph. The values of
and BV for DEAN and
TEAN in aqueous solutions at studied temperatures are collected in Table 4.
3.2
Partial Molar Volume
The partial molar volume of solute (V 2 ) and partial molar volume of solvent (V1 ) of both
studied PILs were calculated from experimental density data using Eqs. (3) and (4) [10,13,33,35]








1000 cV
dV
dV
(3)
V 2 V 
c
d c
2000  c c




d c
M1
V1 
 c
(4)







c
V 2 and V1 data for DEAN and TEAN in aqueous solutions at studied temperatures are
incorporated in Table 2 and Table 3, respectively.
7

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3.3
Coefficient of expansion and apparent molar expansivity
The isobaric expansivity coefficient (α) of studied PILs in aqueous solutions at finite
concentrations were estimated as [11,37]:
1 V
1 

 T






 
 
(5)


V T

P,m
P,m
The calculated values of α for the aqueous solutions of DEAN and TEAN at 293.15 and 298.15
K are reported in Table 2 and 3, respectively.
E
The apparent molar expansivity(  ) can be obtained at 293.15 and 298.15 K using the
Harned and Owen method as [33]:
(0 0)  M 
E 

(6)




m0

where, and

0 are the isobaric expansivity coefficients for solution and solvent, respectively,
0 are the densities (in kg∙m3)of solution and solvent, respectively, and M is the molar
mass of the solute (kg∙mol1).

and


E
The obtained values of  for aqueous solutions of DEAN and TEAN at 293.15 and
298.15 K were collected in Table 2 and 3, respectively.
E
Further,  data can also be expressed as [33]:
E  E0  SEm
where, E0 is the limiting apparent molar expansivity and SE is the limiting slope.
On plotting the graphs of data (calculated with the help of Eq.(6)) as a function of molality
(7)
E
(m/mol∙kg) of DEAN and TEAN in aqueous solutions at 293.15 and 298.15 K(Figs.4 and 5),
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the intercept and slope of the lines results into the values of E0 and SE, respectively, and the data
are collected in Table 4.
The limiting apparent molar expansivity ( 0 ) can also be expressed as [33]:
E
 V0 
0




(8)
E 
 a1  2a2T

T
P
where, a1 and a2 are the differential coefficients, derived on the basis of increase in volume with
rise in temperature.
The calculated values of E0 using Eq. (8) for DEAN and TEAN at all studied temperatures are
also reported in Table 4.
4. Discussion
The density values of the mixtures increase linearly as a function of molality of studied
PILs at all studied temperatures (Table 2 and 3, and Fig. S3 and S4: Supplementary Data). For a
given molality of PILs solutions the densities values decrease as the temperature increases. An
examination of Tables 2 and 3 and Figs. 2 and 3 indicate that, the V values vary little in the
studied concentration region at all studied temperatures. The parameter (V  SV c1/2 ) values also

exhibit small deviations from the DebyeHückel limiting law equation as a function of
concentration , affecting the deviation parameter (BV ) little, for both studied PILs at all studied
temperatures. In our earlier work with imidazolium salts in water with respect to osmotic
coefficients of solutions and mean ionic activity coefficients, we noted that in such solutions
DebyeHückel limiting law is approximately obeyed, exhibiting small differences in volume
values from DebyeHückel limiting law equation for volumes [7]. We confirm such a case for
the volumetric behaviour for the studied PIL's suggesting similar type of ion-solvent interactions
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(ionic hydration). It is known that NO3 a planer anion is water structure breaker [38], while the
hydrophobic cations exhibit negative dependence for volume. Probably there exists a
compensation effect for volume of the salts due to both cation–solvent and anion–solvent
interactions.
The values of limiting apparent molar volume ( 0 ) increase for both the studied PILs as
V
temperature increases (Table 4), which suggests that, the ion–solvent interactions increases as the
V0
temperature increases [11,13]. The
values also increase with increasing the alkyl chain
length/hydrophobicity of cations for a given homologous series [10,11,37]. BV is the deviation
parameter (Eq. (2)), which is generally negative for water structure making ions (Kosmotropic
effect) and positive for water structure breaking ions (Chaotropic effect) [10,11,37,39]. In
present study, we observe small negative BV values for both studied PILs due to hydrophobic
hydration effects and Gurney’s cosphere overlap effects [40] which mean that, the ions of
studied PILs specially cations are water structure making ions at all studied temperatures, except
for DEAN at 288.15 K, for which BV value is small positive in magnitude (Table 4). In fact for
small sized (high charge density) 1:1 electrolytes positive BV values are expected due to
predominance of cation-solvent (chargedipole) interaction effects. This has been nicely
elucidated in the discussion on ionic hydration in the book by Harned and Owen [33]. We could
observe a small positive BV value at low temperature (288.15 K0 for DEAN and almost zero
value at 293.15 K signifying that ion-solvent interaction effects are significantly affected by
charge-density of the cations and temperature. The negative magnitude of BV values increase at
298.15 K and 303.15 K for DEAN and for TEAN at all studied temperatures, the negative
magnitude of BV values increases with increase in temperature, due to hydrophobic interactions
of cation with solvent water/due to solvent enforced ion–pairing (cation–cation interactions) [13]
10

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and cosphere overlap effect [40]. These observations demonstrate that hydrophobic interaction
effects increase with increase in temperature in accordance with the concept of water structure
making hydrophobic hydration of cations (kosmotropic effect).
The individual volumes of the cations have been calculated at 298.15 K as 85.01 and
115.35·10−6 m3∙mol1 for DEAN and TEAN, respectively, by subtracting the anion NO3
contribution as 34.30·10−6 m3∙mol1[38] from the
values of studied PILs at 298.15 K. The
V0
calculation of contribution of increased alkyl groups in TEAN yields the value of 15.17·10−6
m3∙mol1for per methylene group which is in harmony with the results for aqueous solutions of
alkanes, alcohols and amines [41]. It is known that NO3 anion is a water structure breaking
[38,42,43]. Thus the hydration of PILs seem to depend upon both the alkyl group hydration as
well on the basicity of N+ charge centre; along with the nature of anionsolvent interaction. The
observed value also can be rationalized on the basis of Hepler's constant [44] values given in
Table 4.
E
E0
We note from the examination of  (or  ) values, there exists a differentiation in the
mode of interaction of N+ charge centre and alkyl–chain residues with water. It was seen that for
DEAN, the E0 values are similar to those of tetraalkylammonium salts which decrease with
increase in temperature while for TEAN: the values are of lesser in magnitude than DEAN and
increases slightly. Probably, in DEAN, the alkyl residue–water interactions are stronger, while in
case of more symmetric TEAN, the interactions at the N+ charge centre (charge–dipole) also
contribute (in negative direction) with increase in thermal energy. This distinction can be
supported on the basicity of aliphatic amines wherein the introduction of an alkyl group into
ammonia increases the basic strength initially but the third alkyl group causes a decrease in
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basicity. This is due to the fact that the basic strength of an amine in water is determined not only
by electron availability on the nitrogen atom but also by the extent to which the cation, formed
by uptake of a proton, can undergo solvation and so become stabilized. Therefore, our
expansivity results nicely reflect the mode and the role of N+ charge centre in hydration
equilibria in case of DEAN and TEAN.
5.
Conclusions
We have synthesized the two PIL, namely, diethylammonium nitrate [DEAN] and
1
triethylammonium nitrate [TEAN] and characterised their structure by H NMR spectra.
Apparent molar volume and partial molar volume for aqueous solutions of DEAN and TEAN as
a function of concentration at T = 288.15–303.15K have been reported. It is observed that for
both studied PILs, the deviation parameter BV of Debye–Hückel theory for volumes are negative
which means both of them acts as water structure making ions due to the effect of overlap for
solvent cosphere. The single ion partial molar volume of cations are calculated and which are
equal to 85.01 and 115.35·10−6 m3∙mol1 for DEAN and TEAN, respectively.The increment in
volume due to the addition of the methylene group is found to be 15.17·10−6 m3·mol−1. Its seems
that, there is a some compensation effect on volume due to water structure stabilizing influences
of cations and water–structure breaking effect due to anion-water ( NO3 water) interactions.
More studies are required in this direction. The apparent molar expansivity parameter provides
indirectly information about the charge–dipole interactions as well of the alkyl–groups in cations
with surrounding water shell more subtly. Our results thus stress the need of obtaining and
examining the expansivity data for aqueous solutions of model protic ionic liquids.
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Chem. 47 (1969) 4613−4617.
17

ACCEPTED MANUSCRIPT
Captions to the Figures
Fig. 1. Molecular structures of the studied protic ionic liquids.
1/2 ) as a function concentration (c/mol∙dm3) of DEAN
Fig. 2. Variation of parameter 
V  SV c

in aqueous solution: ●, 288.15 K; ▲, 293.15 K; ■, 298.15 K; ♦, 303.15 K.
1/2 ) as a function concentration (c/mol∙dm3) of TEAN in
Fig. 3. Variation of parameter 
V  SV c

aqueous solution: ●, 288.15 K; ▲, 293.15 K; ■, 298.15 K; ♦, 303.15 K.
Fig. 4. Variation of apparent molar expansivity (  )as a function molality (m)of DEAN in
E
aqueous solution at ▲, 293.15 K; ■, 298.15 K.
Fig. 5. Variation of apparent molar expansivity (  )as a function molality (m)of TEAN in
E
aqueous solution at ▲, 293.15 K; ■, 298.15 K.
18

ACCEPTED MANUSCRIPT
Captions to the Tables
Table 1 List of chemical name, CAS number, molecular mass, purity and source of chemicals
used.
Table 2Molality (m), density ( ), apparent molar volume (V ),
1/2 , partial molar
V  SV c


V V
volume of solute ( 2 ), partial molar volume of solvent ( 1 ) and isobaric expansivity (α) data for
aqueous solutions of DEAN at 288.15, 293.15, 298.15, and 303.15 K and apparent molar
expansivity (  ) at 293.15 and 298.15 K and at ambient pressure of 101.325 kPa.a
E
Table 3 Molality (m), density ( ), apparent molar volume (V ),V  SV c1/2 , partial molar


V V
volume of solute ( 2 ), partial molar volume of solvent ( 1 ) and isobaric expansivity (α) data for
aqueous solutions of TEAN at 288.15, 293.15, 298.15, and 303.15 Kand apparent molar
expansivity ( ) at 293.15 and 298.15 K and at ambient pressure of 101.325 kPa.a
Table 4 Limiting apparent molar volume ( 0 ), deviation parameter (BV), limiting apparent
V
2
 V0


molar expansivity ( 0 ), limiting slope and Hepler’s constant (
E
)data for aqueous

T 2

P
solutions of PILs at different temperatures and at ambient pressure of 101.325 kPa.a
19

ACCEPTED MANUSCRIPT
Table 1
Chemical name
CAS No.
Molecular mass
(kg·mol−1)
0.07314
Water Content
(mass fraction)
Mass fraction purity Source
Diethlyamine
Triethylamine
Nitric acid
109–89–7
121–44–8
7697–32–2
≥ 0.99a
≥ 0.99a
> 0.70a
≥ 0.98a
≥ 0.99c
≥ 0.99c
Merck
0.10119
Merck
0.06301
Merck
Phosphorus pentaoxide 1314–56–3
0.14195
Merck
DEANb
TEANb
27096–30–6
27096–31–7
0.13616
0.0025
0.0021
Synthesized in lab
Synthesized in lab
0.16420
aUsed as received without purification.
bAll the PILs used here are synthesized (see section 2.2 below). Diethylammoniumnitrate [DEAN], triethylammonium nitrate [TEAN].
cDried at 343.15 K for 3 days under vacuum in presence of P2O5. The synthesized PIL was dried by applying high vacuum at 323.15 to 328.15 K.
The purity was checked by 1H NMR spectroscopic techniques.
20

ACCEPTED MANUSCRIPT
Table 2
106ϕE
106∙
106∙
)
 a
1/2
ma
/mol∙kg1

∙
/


106∙V 2
106∙V1
V
V  SV c

/m3·mol−1·K−1
/kg∙m3
/m3∙mol1
/m3∙mol1
/m3∙mol1
/m3∙mol1
T = 288.15 K
0.00000 999.104
116.61**
18.031
18.031
0.01923 999.483 116.50±0.16
0.03884 999.863 116.62±0.08
0.06450 1000.335 117.02±0.05
0.07676 1000.559 117.12±0.04
0.09792 1000.910 117.59±0.03
0.13369 1001.588 117.38±0.02
0.16666 1002.142 117.66±0.02
0.19534 1002.664 117.61±0.02
0.24617 1003.507 117.84±0.01
0.29638 1004.398 117.76±0.01
0.34611 1005.240 117.80±0.01
0.39778 1006.087 117.87±0.01
0.44806 1006.921 117.88±0.01
0.50456 1007.856 117.87±0.01
116.26
116.28
116.59
116.65
117.06
116.76
116.98
116.86
117.02
116.86
116.82
116.83
116.78
116.70
116.67±0.16
116.85± 0.08 18.030
117.32± 0.05 18.030
117.45± 0.04 18.030
117.97± 0.03 18.031
117.81± 0.02 18.030
118.14± 0.02 18.031
118.13± 0.01 18.030
118.42± 0.01 18.031
118.39± 0.01 18.031
118.47± 0.01 18.031
118.59± 0.01 18.032
118.64± 0.01 18.032
118.66± 0.01 18.032
T = 293.15 K
0.00000 998.204
117.72**
117.17
118.14
118.55
117.10
117.51
117.67
117.79
117.67
117.60
117.58
117.80
117.60
117.79
117.41
18.047 2.061
117.53± 0.16 18.047 2.110
118.65± 0.08 18.047 2.199
119.20± 0.05 18.048 2.234
117.81± 0.04 18.046 2.175
118.31± 0.03 18.046 2.196
118.61± 0.02 18.047 2.291
118.83± 0.02 18.047 2.297
118.79± 0.01 18.047 2.458
118.86± 0.01 18.047 2.368
118.95± 0.01 18.047 2.584
119.27± 0.01 18.048 2.545
119.17± 0.01 18.048 2.588
119.46± 0.01 18.049 2.693
119.16± 0.01 18.047 2.675
0.01923 998.567 117.42±0.16
0.03884 998.894 118.49±0.08
0.06450 999.314 119.00±0.05
0.07676 999.630 117.59±0.04
0.09792 999.973 118.06±0.03
0.13369 1000.576 118.32±0.02
0.16666 1001.118 118.51±0.02
0.19534 1001.620 118.45±0.02
0.24617 1002.478 118.47±0.01
0.29638 1003.303 118.53±0.01
0.34611 1004.027 118.83±0.01
0.39778 1004.906 118.70±0.01
0.44806 1005.601 118.96±0.01
0.50456 1006.634 118.64±0.01
0.2775
0.3823
0.2946
0.1749
0.1641
0.1993
0.1691
0.2326
0.1530
0.2075
0.1704
0.1635
0.1732
0.1536
T = 298.15 K
0.00000 997.045
119.41**
119.37
120.17
119.42
118.58
118.79
18.068 2.566
119.60± 0.16 18.068 2.594
120.49± 0.08 18.069 2.678
119.83± 0.05 18.069 2.641
119.04± 0.04 18.068 2.665
119.31± 0.03 18.068 2.724
0.01923 997.368 119.63±0.16
0.03884 997.661 120.54±0.08
0.06450 998.106 119.89±0.05
0.07676 998.366 119.09±0.04
0.09792 998.699 119.37±0.03
0.1794
0.3217
0.1485
0.1612
0.1940
21

ACCEPTED MANUSCRIPT
0.13369 999.283 119.46±0.02
118.78
118.64
119.41
118.57
119.05
118.44
118.41
118.37
118.17
119.38± 0.02 18.068 2.727
0.1535
0.1400
0.1320
0.1267
0.1460
0.0926
0.1195
0.1131
0.1175
0.16666 999.835 119.39±0.02
0.19534 1000.146 120.22±0.02
0.24617 1001.107 119.48±0.01
0.29638 1001.743 120.05±0.01
0.34611 1002.680 119.51±0.01
0.39778 1003.465 119.56±0.01
0.44806 1004.224 119.59±0.01
0.50456 1005.139 119.46±0.01
119.31± 0.02 18.068 2.744
120.13± 0.02 18.071 2.758
119.38± 0.01 18.068 2.795
119.94± 0.01 18.071 2.895
119.39± 0.01 18.068 2.771
119.43± 0.01 18.068 2.902
119.45± 0.01 18.068 2.915
119.32± 0.01 18.067 2.978
T = 303.15 K
0.00000 995.644
119.90**
119.30
121.42
119.92
118.88
119.53
119.23
119.16
119.20
118.89
119.16
118.64
118.74
118.78
118.51
18.094
119.51± 0.16 18.094
121.72± 0.08 18.095
120.30± 0.05 18.094
119.31± 0.04 18.093
120.01± 0.03 18.094
119.78± 0.02 18.094
119.78± 0.02 18.094
119.87± 0.02 18.094
119.64± 0.01 18.093
0.01923 995.971 119.57±0.16
0.03884 996.217 121.80±0.08
0.06450 996.681 120.41±0.05
0.07676 996.951 119.42±0.04
0.09792 997.238 120.14±0.03
0.13369 997.838 119.94±0.02
0.16666 998.367 119.95±0.02
0.19534 998.805 120.05±0.02
0.24617 999.654 119.84±0.01
0.29638 1000.341 120.20±0.01
0.34611 1001.244 119.76±0.01
0.39778 1001.973 119.94±0.01
0.44806 1002.684 120.06±0.01
0.50456 1003.616 119.86±0.01
119.98±0.01
18.095
119.52± 0.01 18.093
119.69± 0.01 18.094
119.79± 0.01 18.095
119.58± 0.01 18.093
aStandard uncertainties uareu= 0.01 K, up= 0.3kPa, um= 5·10−5 mol·kg−1. The
combined uncertainties uc= 3∙103kg∙m3, ucV1 = 2∙109m3∙molucα= 3∙107K1 and uc(
E ) = 2.10−9 m3.mol−1.K−1.

**Extrapolated value at infinitely dilute solution of IL's in water at 288.15, 293.15, 298.15 and
303.15 K.
22

ACCEPTED MANUSCRIPT
Table 3
106∙
106∙
)
 a
1/2
ma
/mol∙kg1

∙
/
106ϕE


106∙V 2
106∙V1
V
V  SV c

/m3·mol−1·K−1
/kg∙m3
/m3∙mol1
/m3∙mol1
/m3∙mol1
/m3∙mol1
T = 288.15 K
0.00000 999.104
148.19**
148.06
148.13
148.14
148.13
148.17
148.14
148.09
148.08
148.01
147.98
147.92
147.90
147.82
147.77
18.031
148.38± 0.015 18.031
0.01991 999.422 148.30±0.15
0.03720 999.691 148.45±0.08
0.05696 999.995 148.54±0.05
0.07729 1000.305 148.60±0.04
0.09748 1000.605 148.70±0.03
0.12802 1001.061 148.74±0.02
0.16978 1001.678 148.78±0.02
0.19761 1002.078 148.83±0.02
0.25390 1002.890 148.84±0.01
0.29805 1003.510 148.88±0.01
0.35177 1004.258 148.90±0.01
0.39754 1004.876 148.94±0.01
0.45221 1005.629 148.92±0.01
0.51256 1006.430 148.94±0.01
148.55± 0.08
148.67± 0.05
148.75± 0.04
148.86± 0.03
148.93± 0.02
148.99± 0.02
149.05± 0.02
149.10± 0.01
149.15± 0.01
149.19± 0.01
149.25± 0.01
149.24± 0.01
149.28± 0.01
18.031
18.031
18.031
18.031
18.031
18.031
18.031
18.031
18.031
18.031
18.031
18.031
18.031
T = 293.15 K
0.00000 998.204
149.11**
149.03
149.04
149.04
149.00
148.99
148.99
148.95
148.91
148.81
148.79
148.67
148.63
148.54
148.53
18.047 2.061
149.33± 0.015 18.047 2.090
0.01991 998.505 149.28±0.15
0.03720 998.761 149.39±0.08
0.05696 999.050 149.46±0.05
0.07729 999.346 149.50±0.04
0.09748 999.636 149.54±0.03
0.12802 1000.066 149.62±0.02
0.16978 1000.650 149.67±0.02
0.19761 1001.035 149.69±0.02
0.25390 1001.812 149.69±0.01
0.29805 1002.400 149.74±0.01
0.35177 1003.130 149.70±0.01
0.39754 1003.730 149.72±0.01
0.45221 1004.450 149.70±0.01
0.51256 1005.194 149.76±0.01
0.1762
0.1670
0.1641
0.1615
0.1565
0.1566
0.1587
0.1548
0.1557
0.1519
0.1506
0.1512
0.1545
0.1520
149.46± 0.08
149.55± 0.05
149.60± 0.04
149.65± 0.03
149.75± 0.03
149.82± 0.02
149.86± 0.01
149.87± 0.01
149.93± 0.01
149.91± 0.01
149.94± 0.01
149.93± 0.01
150.00± 0.01
18.047 2.111
18.047 2.136
18.047 2.161
18.047 2.181
18.047 2.219
18.047 2.272
18.047 2.298
18.047 2.366
18.048 2.406
18.047 2.460
18.047 2.512
18.047 2.584
18.048 2.637
T = 298.15 K
0.00000 997.045
149.75**
149.73
149.70
149.69
149.65
18.068 2.566
18.068 2.597
18.068 2.618
18.068 2.637
18.068 2.665
0.01991 997.335 149.99±0.15
0.03720 997.583 150.06±0.08
0.05696 997.862 150.14±0.05
0.07729 998.148 150.17±0.04
150.05± 0.15
150.13± 0.08
150.23± 0.05
150.27± 0.04
0.1938
0.1799
0.1643
0.1689
23

ACCEPTED MANUSCRIPT
0.09748 998.426 150.23±0.03
0.12802 998.847 150.26±0.02
0.16978 999.411 150.31±0.02
0.19761 999.784 150.33±0.02
0.25390 1000.528 150.36±0.01
0.29805 1001.111 150.35±0.01
0.35177 1001.797 150.38±0.01
0.39754 1002.360 150.44±0.01
0.45221 1003.035 150.46±0.01
0.51256 1003.791 150.43±0.01
149.65
149.59
149.55
149.51
149.44
149.35
149.30
149.29
149.24
149.14
150.35± 0.03
150.39± 0.02
150.47± 0.02
150.50± 0.02
150.55± 0.01
150.55± 0.01
150.60± 0.01
150.66± 0.01
150.70± 0.01
150.68± 0.01
18.068 2.684
18.068 2.719
18.068 2.765
18.068 2.785
18.068 2.862
18.068 2.891
18.068 2.944
18.069 3.013
18.069 3.071
18.069 3.088
0.1618
0.1608
0.1594
0.1533
0.1598
0.1530
0.1520
0.1581
0.1582
0.1486
T = 303.15 K
0.00000 995.644
150.76**
150.87
150.75
150.59
150.60
150.52
150.48
150.42
150.33
150.29
150.18
150.07
150.09
150.00
149.87
18.094
18.094
18.094
18.094
18.094
18.094
18.094
18.094
18.094
18.094
18.094
18.094
18.094
18.094
18.094
0.01991 995.915 151.15±0.15
0.03720 996.150 151.12±0.08
0.05696 996.420 151.06±0.05
0.07729 996.688 151.13±0.04
0.09748 996.958 151.12±0.03
0.12802 997.355 151.18±0.02
0.16978 997.893 151.21±0.02
0.19761 998.257 151.18±0.02
0.25390 998.957 151.25±0.01
0.29805 999.518 151.22±0.01
0.35177 1000.188 151.20±0.01
0.39754 1000.715 151.28±0.01
0.45221 1001.371 151.27±0.01
0.51256 1002.106 151.22±0.01
151.17± 0.15
151.15± 0.08
151.09± 0.05
151.17± 0.04
151.17± 0.03
151.23± 0.02
151.27± 0.02
151.25± 0.02
151.32± 0.01
151.29± 0.01
151.28± 0.01
151.37± 0.01
151.36± 0.01
151.31± 0.01
aStandard uncertainties uareu= 0.01 K, up= 0.3 kPa,um= 5·10−5 mol·kg−1. The
combined uncertainties uc= 3∙103kg∙m3, ucV1 = 2∙109m3∙mol, ucα= 3∙107K1 and uc(
E ) = 2.10−9 m3.mol−1.K−1.

**Extrapolated value at infinitely dilute solution of IL's in water at 288.15, 293.15, 298.15 and
303.15 K.
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Table 4
106∙
106∙
E
 V0


2
0
0
E
106
0
106∙SE /
106BV
V


T 2
/m3∙mol1∙K1
/m3∙mol1∙K1
T/ K
m6mol2∙K1
/ m6mol2
P
/ m3mol1
/m3∙mol1∙K2
(Eq. (8))
(Eq. (7))
1.24·10−2
DEAN
288.15
293.15
298.15
303.15
116.61 ± 0.10
117.72 ± 0.17
119.41 ± 0.19
119.90 ± 0.27
0.324 ± 0.0003
0.262± 0.0004
0.200± 0.0003
0.138± 0.0003
± 0.42
25 ± 0.70
2.60 ± 0.74
3.18 ± 1.06
± 0.025
± 0.020
25 ± 0.09
22 ± 0.07
0.18·10−2
TEAN
288.15
293.15
298.15
303.15
148.19 ± 0.02
149.11 ± 0.02
149.75 ± 0.01
150.76 ± 0.03
± 0.08
± 0.06
± 0.03
± 0.12
± 0.0001
± 0.0001
± 0.0001
0.181± 0.0002


± 0.002
± 0.003
03 ± 0.008
05 ± 0.014
aStandard uncertainties uare u= 0.01 K, up= 0.3kPa.
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N
-O
+
H2
O-
O
N+
NH+
N+
O-
O-
O
Diethylammonium Nitrate
Triethylammonium Nitrate
Fig. 1.
130
125
120
115
110
105
100
130
125
120
115
110
105
100
130
125
120
115
110
105
100
130
125
120
115
110
105
100
0.0
0.1
0.2
0.3
0.4
0.5
c/mol·dm−3
Fig. 2.
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160
155
150
145
140
135
160
155
150
145
140
135
160
155
150
145
140
135
160
155
150
145
140
135
0.0
0.1
0.2
0.3
0.4
0.5
c/mol·dm−3
Fig. 3.
1.5
1.0
0.5
0.0
0.0
0.1
0.2
0.3
0.4
0.5
1.5
1.0
0.5
0.0
0.0
0.1
0.2
0.3
0.4
0.5
m /mol·kg−1
Fig. 4.
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0.6
0.3
0.0
0.6
0.3
0.0
0.0
0.1
0.2
0.3
0.4
0.5
m /mol·kg−1
Fig. 5.
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Graphical Abstract:
Figure: Variation of limiting apparent molar expansivity (
diethylammonium nitrate (DEAN) and triethylammonium nitrate (TEAN).
E
0 ) as a function of temperature for
29