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Comments on “Molecular interactions in the binary mixtures of some monoalkanolamines with acetonitrile between 303.15 and 323.15”
MOLLIQ-112180; No of Pages 2 Journal of Molecular Liquids xxx (xxxx) xxx
Contents lists available at ScienceDirect
Journal of Molecular Liquids journal homepage: www.elsevier.com/locate/molliq
Short Communication
Comments on “Molecular interactions in the binary mixtures of some monoalkanolamines with acetonitrile between 303.15 and 323.15” William E. Acree Jr Department of Chemistry, University of North Texas, Denton, TX 76203, USA
a r t i c l e
i n f o
a b s t r a c t
Article history: Received 16 October 2019 Accepted 20 November 2019 Available online xxxx
Errors were noted pertaining to the volumetric properties reported in the published paper by Khan and coworkers. Excess molar volumes reported in the paper were found to be inconsistent with the partial molar volumes of the individual mixture components. Experimental densities reported in the paper were also found to be inconsistent with the partial molar volumes of the mixture components. © 2019 Elsevier B.V. All rights reserved.
Keywords: Excess molar volumes Partial molar volumes Thermodynamic consistency test
In a recent paper published in the Journal of Molecular Liquids Khan and coworkers [1] reported the experimental densities, ρ, and refractive indices, nD, of binary mixtures containing acetonitrile with monoethanolamine, monomethylethanolamine, and monoethylethanolamine. For each of the three binary systems densities were measured over the enter mole fraction concentration range and at five different temperatures. The authors calculated the excess molar volumes, VEm, at each temperature and mole fraction composition, as well as the partial molar volumes of the two individual mixture components, V 1 and V 2 . Unfortunately, the authors' calculated partial molar volumes that are given in Table 4 of their published paper [1] are not thermodynamically consistent with the VEmvalues tabulated in Table 3 [1]. Excess molar volumes are related to partial molar volumes of the individual mixture components through the following standard thermodynamic relationship: 0 0 V Em ¼ x1 V 1 −V 1 þ x2 V 2 −V 2
MM1 MM 2 þ x2 V 2 − V Em ¼ x1 V 1 − ρ1 ρ2 0:0410519 V Em ¼ 0:8500 0:000052430− 771:10 0:0751097 þ0:1500 0:000067759− 934:33
ð2Þ
ð3Þ
ð1Þ
where x1 and x2 denote the mole fractions of mixture components 1 and 0
molar mass of the respective component divided by its density at temperature T. To show the thermodynamic inconsistencies I will calculate VEm for the binary acetonitrile (1) + monomethylethanolamine (2) system at x2 = 0.1500 and T = 303.15 K by substituting the molar masses (MM1 = 0.0410519 kg·mol−1 and MM2 = 0.0751097 kg·mol−1), the densities (ρ = 771.10 kg·m−3 and 934.33 kg·m−3), and partial molar volumes (106⋅ V 1 = 52.430 m3·mol−1 and 106· V 2 = 67.759 m3·mol−1) into the equation below:
0
2, and V 1 and V 2 represent the molar volumes of the two pure mixture 0
0
components. The numerical values of V 1 and V 2 are calculated as the
E-mail address: [email protected].
Performing the indicated mathematical computations I calculate a numerical value of 106⋅VEm = −2.58 m3·mol−1, which differs significantly from the value of 106⋅VEm = −0.776 m3·mol−1 that the authors gave in Table 3 of their published paper [1]. I spot checked several other sets of values for thermodynamic consistency. All sets of values that I checked were also found to be thermodynamically inconsistent. The values did not obey Eq. (1) of this commentary. These errors could have been easily avoided had the authors carefully checked their calculated values for thermodynamic consistency using Eq. (1).
https://doi.org/10.1016/j.molliq.2019.112180 0167-7322/© 2019 Elsevier B.V. All rights reserved.
Please cite this article as: W.E. Acree, Comments on “Molecular interactions in the binary mixtures of some monoalkanolamines with acetonitri..., Journal of Molecular Liquids, https://doi.org/10.1016/j.molliq.2019.112180
2
W.E. Acree Jr / Journal of Molecular Liquids xxx (xxxx) xxx
I also checked the authors' calculated partial molar volumes to make sure that the values were consistent with experimental densities given in Table 3 of the published paper [1]. The mole fraction average of the partial molar volumes should equal the molar volume of the binary mixture calculated using: x1 MM1 þ x2 MM2 ¼ x1 V 1 þ x2 V 2 ρ
ð4Þ
the molar masses of the individual mixture components and the density of the binary mixture. I substitute the numerical values of the molar masses of acetonitrile and monomethylethanolamine, and the density and partial molar volumes of acetonitrile and mommethylethanolamine of the binary acetonitrile (1) + monomethylethanolamine (2) system at x2 = 0.1500 and T = 303.15 K into Eq. (4) to obtain:
0:000056535 m3 mol
−1
¼ 0:000054729 m3 mol
−1
ð6Þ
I found that the left-hand and right-hand sides of Eqs. (5) and (6) are different. The mathematical equality required by Eq. (5) is not obeyed. There are major errors in the volumetric properties reported in the published paper by Khan and coworkers [1].
References [1] M.A.R. Khan, M.M.H. Rocky, F.I. Chowdhury, M.S. Ahmed, S. Akhtar, Molecular interactions in the binary mixtures of some monoalkanolamines with acetonitrile between 303.15 and 323.15, J. Mol. Liq. 277 (2019) 681–691.
ð0:8500Þð0:0410519Þ þ ð0:1500Þð0:0751097Þ ¼ 0:8500 ð0:000052430Þ 816:5 þ 0:1500 ð0:000067759Þ ð5Þ
Please cite this article as: W.E. Acree, Comments on “Molecular interactions in the binary mixtures of some monoalkanolamines with acetonitri..., Journal of Molecular Liquids, https://doi.org/10.1016/j.molliq.2019.112180
Contents lists available at ScienceDirect
Journal of Molecular Liquids journal homepage: www.elsevier.com/locate/molliq
Short Communication
Comments on “Molecular interactions in the binary mixtures of some monoalkanolamines with acetonitrile between 303.15 and 323.15” William E. Acree Jr Department of Chemistry, University of North Texas, Denton, TX 76203, USA
a r t i c l e
i n f o
a b s t r a c t
Article history: Received 16 October 2019 Accepted 20 November 2019 Available online xxxx
Errors were noted pertaining to the volumetric properties reported in the published paper by Khan and coworkers. Excess molar volumes reported in the paper were found to be inconsistent with the partial molar volumes of the individual mixture components. Experimental densities reported in the paper were also found to be inconsistent with the partial molar volumes of the mixture components. © 2019 Elsevier B.V. All rights reserved.
Keywords: Excess molar volumes Partial molar volumes Thermodynamic consistency test
In a recent paper published in the Journal of Molecular Liquids Khan and coworkers [1] reported the experimental densities, ρ, and refractive indices, nD, of binary mixtures containing acetonitrile with monoethanolamine, monomethylethanolamine, and monoethylethanolamine. For each of the three binary systems densities were measured over the enter mole fraction concentration range and at five different temperatures. The authors calculated the excess molar volumes, VEm, at each temperature and mole fraction composition, as well as the partial molar volumes of the two individual mixture components, V 1 and V 2 . Unfortunately, the authors' calculated partial molar volumes that are given in Table 4 of their published paper [1] are not thermodynamically consistent with the VEmvalues tabulated in Table 3 [1]. Excess molar volumes are related to partial molar volumes of the individual mixture components through the following standard thermodynamic relationship: 0 0 V Em ¼ x1 V 1 −V 1 þ x2 V 2 −V 2
MM1 MM 2 þ x2 V 2 − V Em ¼ x1 V 1 − ρ1 ρ2 0:0410519 V Em ¼ 0:8500 0:000052430− 771:10 0:0751097 þ0:1500 0:000067759− 934:33
ð2Þ
ð3Þ
ð1Þ
where x1 and x2 denote the mole fractions of mixture components 1 and 0
molar mass of the respective component divided by its density at temperature T. To show the thermodynamic inconsistencies I will calculate VEm for the binary acetonitrile (1) + monomethylethanolamine (2) system at x2 = 0.1500 and T = 303.15 K by substituting the molar masses (MM1 = 0.0410519 kg·mol−1 and MM2 = 0.0751097 kg·mol−1), the densities (ρ = 771.10 kg·m−3 and 934.33 kg·m−3), and partial molar volumes (106⋅ V 1 = 52.430 m3·mol−1 and 106· V 2 = 67.759 m3·mol−1) into the equation below:
0
2, and V 1 and V 2 represent the molar volumes of the two pure mixture 0
0
components. The numerical values of V 1 and V 2 are calculated as the
E-mail address: [email protected].
Performing the indicated mathematical computations I calculate a numerical value of 106⋅VEm = −2.58 m3·mol−1, which differs significantly from the value of 106⋅VEm = −0.776 m3·mol−1 that the authors gave in Table 3 of their published paper [1]. I spot checked several other sets of values for thermodynamic consistency. All sets of values that I checked were also found to be thermodynamically inconsistent. The values did not obey Eq. (1) of this commentary. These errors could have been easily avoided had the authors carefully checked their calculated values for thermodynamic consistency using Eq. (1).
https://doi.org/10.1016/j.molliq.2019.112180 0167-7322/© 2019 Elsevier B.V. All rights reserved.
Please cite this article as: W.E. Acree, Comments on “Molecular interactions in the binary mixtures of some monoalkanolamines with acetonitri..., Journal of Molecular Liquids, https://doi.org/10.1016/j.molliq.2019.112180
2
W.E. Acree Jr / Journal of Molecular Liquids xxx (xxxx) xxx
I also checked the authors' calculated partial molar volumes to make sure that the values were consistent with experimental densities given in Table 3 of the published paper [1]. The mole fraction average of the partial molar volumes should equal the molar volume of the binary mixture calculated using: x1 MM1 þ x2 MM2 ¼ x1 V 1 þ x2 V 2 ρ
ð4Þ
the molar masses of the individual mixture components and the density of the binary mixture. I substitute the numerical values of the molar masses of acetonitrile and monomethylethanolamine, and the density and partial molar volumes of acetonitrile and mommethylethanolamine of the binary acetonitrile (1) + monomethylethanolamine (2) system at x2 = 0.1500 and T = 303.15 K into Eq. (4) to obtain:
0:000056535 m3 mol
−1
¼ 0:000054729 m3 mol
−1
ð6Þ
I found that the left-hand and right-hand sides of Eqs. (5) and (6) are different. The mathematical equality required by Eq. (5) is not obeyed. There are major errors in the volumetric properties reported in the published paper by Khan and coworkers [1].
References [1] M.A.R. Khan, M.M.H. Rocky, F.I. Chowdhury, M.S. Ahmed, S. Akhtar, Molecular interactions in the binary mixtures of some monoalkanolamines with acetonitrile between 303.15 and 323.15, J. Mol. Liq. 277 (2019) 681–691.
ð0:8500Þð0:0410519Þ þ ð0:1500Þð0:0751097Þ ¼ 0:8500 ð0:000052430Þ 816:5 þ 0:1500 ð0:000067759Þ ð5Þ
Please cite this article as: W.E. Acree, Comments on “Molecular interactions in the binary mixtures of some monoalkanolamines with acetonitri..., Journal of Molecular Liquids, https://doi.org/10.1016/j.molliq.2019.112180