Measurement of Solubility of Thiamine Hydrochloride Hemihydrate in

Article pubs.acs.org/jced

Measurement of Solubility of Thiamine Hydrochloride Hemihydrate in Three Binary Solvents and Mixing Properties of Solutions Xiaona Li,†,‡ Dandan Han,†,‡ Yan Wang,†,‡ Shichao Du,†,‡ Yumin Liu,†,‡ Jiaqi Zhang,† Bo Yu,†,‡ Baohong Hou,†,‡ and Junbo Gong*,†,‡ †

State Key Laboratory of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, People’s Republic of China ‡ The Collaborative Innovation Center of Chemical Science and Engineering of Tianjin, Tianjin University, Tianjin 300072, People’s Republic of China S Supporting Information *

ABSTRACT: Data on (solid + liquid) equilibrium of thiamine hydrochloride hemihydrate (HH) in {water + (ethanol, acetone, or 2-propanol)} solvents will provide essential support for industrial design and further theoretical studies. In this study the solid−liquid equilibrium (SLE) was experimentally measured over temperatures ranging from 278.15 to 313.15 K under atmospheric pressure by a dynamic method. For the temperature range investigated, the equilibrium solubility of thiamine hydrochloride hemihydrate (HH) varies with temperature and the composition of the solvents. The experimental solubility was regressed with different models including the modified Apelblat equation, λh equation, as well as NRTL equation. All the models gave good agreements with the experimental results. On the basis of the solubility data of HH, the thermodynamic properties of mixing process of HH with mixed solvents were also discussed. The results indicate that the mixing process of HH is exothermic. Besides, the model outwardly like the Arrhenius equation was employed to quantitatively exhibit the relationship between solubility and solvents mixtures polarity of solvents mixtures. Up to now, there exist five solid-state forms of thiamine hydrochloride reported in the literature.7−9 According to the literature, thiamine hydrochloride hemihydrate (HH) is the most stable form in contact with water. Once formed, the dehydration is initiated only when heated to 120 °C.10,11 Because the crucial role of thiamine hydrochloride in the industry, it is necessary to find a suitable solvent for its separation and subsequent recrystallization to achieve the industrial scale synthesis with high purity. However, despite the fact that people have investigated much about the transformation among the five forms of thiamine hydrochloride, only a few have attempted to discuss its purification methods to obtain products with high yield and high purity. Solution crystallization is used as the separation and purification method in the manufacturing process of thiamine hydrochloride. Therefore, detailed solubility data and thermodynamic properties of thiamine hydrochloride in different solvent systems are crucial to fully understand and design a reliable crystallization process for its purification. Data on (solid + liquid) equilibrium of thiamine hydrochloride hemihydrate (HH) in {water + (ethanol, acetone, or 2-propanol)} solvents will provide essential support for industrial design and further theoretical studies. Thus, the aim of the present work is to

1. INTRODUCTION Crystallization is one of the most common operations used in the separation and purification, especially in the cases of pharmaceuticals, foods additives and biological macromolecular foods.1 The solubility of pharmaceuticals in selected solvents is critical for identification of drugs to develop more efficient active pharmaceutical ingredients. The quality of the final product, such as crystal size, crystal habit, yield, and purity, will be directly determined by the level of design and control of crystallization process.2 Thiamine hydrochloride (VB1, C12H18Cl2N4OS, CAS Registry No. 67-03-08, Figure 1) plays an important role in digestive

Figure 1. Molecular structure of thiamine hydrochloride.

system, nerve conduction and normal heart activity.3−5 It is mainly used in animal feed and nutrient supplements in feed industries, medicines, cosmetics, other industries, and so on.6,7 © XXXX American Chemical Society

Received: July 10, 2016 Accepted: September 6, 2016

A

DOI: 10.1021/acs.jced.6b00613 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

light intensity and concentration of particles in suspension. All experiments were carried out in a 50 mL jacketed glass vessel with a magnetic stirrer applied as dissolver. A mercury-in-glass thermometer with uncertainty of ±0.1 K inside the vessel displayed the real temperature. The circulating water bath (CHY1015, Shanghai Shunyu Hengping Scientific Instrument Co. Ltd., China) was introduced to the apparatus to control temperature maintaining the setting temperature within the error range of ±0.1 K. The transmitted laser (JD-3, Department of Peking University, China) was employed to observe the dissolution by the change of the intensity of the solution. The solute and solvents were weighted by an electronic analytical balance (AL204, Meteler Toledo, Switzerland) with an accuracy of ±0.0001 g. At a fixed temperature, predetermined masses of solvents (50 mL) were added into the jacketed vessel. A condenser was employed to prevent the evaporation of the solvents. A fixed amount of HH was added into the vessel when the temperature was stable. At first, the laser beam was blocked by the undissolved particles in the solution, so the intensity of laser beam through the vessel was low. The intensity increases gradually with the dissolution of the solute. When the HH just disappeared, the intensity reached the maximum. Then an additional solute of

determine the solubility of the most stable form HH in the three binary solvents at temperatures ranging from 278.15 to 313.15 K by the gravimetric method. The Apelblat equation, λh equation and NRTL equation were adopted to correlate the solubility data. On the basis of the NRTL equation, the thermodynamic properties of mixing process for the solutions of HH in binary solvents were calculated, respectively. Finally, the form outwardly like the Arrhenius equation was applied to quantitatively correlate the solubility of HH and the dielectric constant of the binary solvents.

2. EXPERIMENTAL SECTION 2.1. Materials. All the organic solvents with analytical grade (ethanol, 2-propanol, and acetone) were purchased from Tianjin Kewei Reagents Co. Ltd. (Tianjin, China) and used without further purification. The thiamine hydrochloride, with mass fraction purity higher than 0.99, was purchased from Aladdin Industrial Co. (Shanghai, China). It was characterized to be nonstoichiometric hydrate thiamine hydrochloride (NSH) by X-ray diffraction. According to the literature, HH powder was obtained by suspending NSH in water for 12 h at 40 °C, then the product was dried at 40 °C for 24 h.10 Ultrapure water (resistivity = 18.2 MΩ cm) used throughout the measurement process was prepared in our laboratory. The detailed information on the chemicals used in the present work can be found in Table 1. Table 1. Sources and Mass Fraction Purity of Materialsa,b mass fraction chemical name purity

source

thiamine ≥0.990 Aladdin Industrial Co., hydrochloride China ethanol >0.997 Tianjin Kewei Chemical Co., China 2-propanol >0.997 Tianjin Kewei Chemical Co., China acetone >0.997 Tianjin Kewei Chemical Co., China a

purification method

analysis method

recrystallized

HPLCa

none

GCb

none

GCb

none

GCb

High performance liquid chromatography. bGas chromatography.

2.2. Apparatus and Procedure. 2.2.1. Characterization by X-ray Diffraction. First, the prepared powder by suspending method according to the literature was measured by X-ray diffraction. To ensure there was no form transformation among the five hydrates during our process of solubility measurement, we put excess solid of HH into all experimental compositions and temperatures, respectively. The suspension was sure to be agitated for 24 h the time of which is enough for our measurement at a certain temperature. Then the X-ray spectra of the sediments were measured by Cu Kα radiation (1.54). The condition was on 2θ = 2−50° with a step size of 0.02°. Then the scanning rate was set at 1 step/s.8,11 2.2.2. Characterization by TGA/DSC. TGA/DSC (Model TGA/DSC, Mettler-Toledo, Switzerland) was formed to get thermal analysis of HH under the protection of nitrogen. The measurements were carried out under the protection of nitrogen with a heating rate of 10 K/min. The amount of sample used was about 5−10 mg. 2.2.3. Solubility Determination. The laser monitoring technique was used to determine the solubility of HH. The apparatus were similar to that had been described in the literatures.12,13 The method is based on the Lambert−Beer Law, which correlates

Figure 2. Powder X-ray diffraction (PXRD) patterns for excess solid of VB1 in different conditions: (a = purchased materials; b = prepared materials; c, d, e = sediments in binary solvents water (xwater = 0.10, 0.50, 0.90) + ethanol at T = 313.15 K, respectively).

Figure 3. Thermal analysis (TGA/DSC) of HH. B



Article

Table 2. Mole Fraction Solubility of HH in the Binary Ethanol + Water Solvent Mixtures at Different Temperatures from 278.15 to 313.15 K at p = 0.1 MPaa,b,c,d,e x0B

103 xaexp

x0B

103 xAexp

0.000 0.099 0.198 0.298 0.398 0.499 0.599 0.700 0.800

38.58 27.21 19.45 12.97 8.59 5.15 2.55 1.19 0.54

0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800

39.34 27.59 19.59 13.03 8.63 5.17 2.55 1.19 0.55

0.000 0.098 0.198 0.298 0.398 0.499 0.599 0.700 0.800

40.97 31.13 22.57 15.28 10.02 5.63 2.98 1.37 0.60

0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800

41.83 31.62 22.82 15.54 10.07 5.65 2.99 1.37 0.60

0.000 0.098 0.197 0.297 0.398 0.498 0.599 0.699 0.800

43.24 33.08 24.59 17.40 11.48 6.57 3.42 1.54 0.66

0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800

44.19 33.64 24.95 17.59 11.54 6.59 3.42 1.54 0.66

0.000 0.098 0.197 0.297 0.397 0.498 0.599 0.699 0.800

46.20 38.23 29.92 21.43 14.14 8.24 4.16 1.92 0.82

0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800

47.30 38.97 30.00 21.60 14.24 8.27 4.17 1.92 0.82

0.000 0.098 0.197 0.296 0.397 0.498 0.598 0.699 0.800

48.27 41.87 33.63 24.82 16.64 9.82 5.09 2.34 0.95

0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800

49.47 42.77 34.12 25.22 16.78 9.87 5.10 2.34 0.96

0.000 0.098 0.196 0.296 0.396 0.497 0.598 0.699 0.800

50.43 42.92 34.55 25.76 17.51 10.33 5.27 2.48 1.02

0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800

51.74 43.86 35.15 26.05 17.66 10.39 5.29 2.48 1.02

103 xAcal(Apelbat)

103 xAcal(λh)

103 xacal(NRTL)

39.77 27.76 19.57 13.04 8.59 5.05 2.52 1.18 0.52

39.16 28.82 20.51 13.86 8.88 4.90 2.62 1.16 0.54

39.16 27.88 19.79 12.93 8.33 4.99 2.74 1.44 0.59

41.75 31.22 22.71 15.57 10.20 5.88 3.01 1.38 0.62

41.62 31.54 23.04 15.89 10.32 5.81 3.05 1.38 0.62

40.87 31.31 22.84 15.27 9.74 5.55 3.13 1.61 0.65

43.98 34.71 25.98 18.26 11.96 6.84 3.55 1.62 0.71

44.19 34.43 25.79 18.14 11.92 6.86 3.54 1.62 0.71

42.96 33.38 24.96 17.50 11.25 6.44 3.55 1.81 0.72

46.46 38.17 29.32 21.07 13.87 7.97 4.15 1.89 0.82

46.87 37.50 28.77 20.61 13.72 8.05 4.09 1.89 0.81

45.11 37.53 29.60 21.35 13.81 7.90 4.16 2.08 0.82

49.22 41.55 32.69 23.95 15.92 9.29 4.78 2.20 0.92

49.66 40.75 31.98 23.33 15.71 9.40 4.71 2.21 0.91

47.98 40.78 32.89 24.61 16.31 9.39 4.92 2.38 0.92

52.28 44.79 36.01 26.83 18.10 10.82 5.45 2.55 1.04

52.58 44.20 35.46 26.31 17.91 10.92 5.39 2.56 1.03

51.18 42.95 34.58 26.10 17.58 10.20 5.34 2.63 1.02

T = 278.15 K

T = 283.15 K

T = 288.15 K

T = 293.15 K

T = 298.15 K

T = 303.15 K

C



Article

Table 2. continued x0B

103 xaexp

x0B

103 xAexp

0.000 0.098 0.196 0.296 0.396 0.497 0.598 0.699 0.800

52.79 45.82 37.38 28.52 19.42 12.24 5.99 2.86 1.17

0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800

54.22 46.89 38.18 28.68 19.61 12.31 6.01 2.87 1.17

0.000 0.097 0.196 0.295 0.395 0.496 0.598 0.699 0.799

58.69 50.10 42.11 32.42 22.79 14.78 6.97 3.45 1.26

0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800

60.46 51.38 43.02 32.99 23.22 14.89 6.99 3.46 1.26

103 xAcal(Apelbat)

103 xAcal(λh)

103 xacal(NRTL)

55.67 47.85 39.24 29.64 20.38 12.60 6.16 2.95 1.15

55.63 47.85 39.19 29.57 20.35 12.63 6.15 2.95 1.15

54.70 46.28 37.58 29.04 19.78 12.09 6.09 2.99 1.15

59.40 50.68 42.31 32.34 22.75 14.68 6.89 3.41 1.27

58.81 51.71 43.20 33.12 23.03 14.54 6.98 3.40 1.29

57.15 50.42 41.67 32.79 23.17 14.54 7.05 3.45 1.28

T = 308.15 K

T = 313.15 K

the initial mole fraction of ethanol in the binary solvent mixture; ax0Bis the final mole fraction of ethanol in the binary solvent mixture;xexp A is the experimentally determined solubility based on thiamine hydrochloride in soultions; xexp A is the experimentally determined solubility based on HH in cal exp cal soultions; xcal A (Apelbat) and xA (λh) are the calculated solubility by Apelbat and λh based on xA , respectively. xA (NRTL) are the calculated b c solubility by NRTL equation based on xexp A . The standard uncertainty of temperature is uc(T) = 0.1 K. The relative standard uncertainty of the solubility measurement is ur(x) = 0.02. dThe relative uncertainty of pressure is ur(P) = 0.05. eThe relative standard uncertainty in mole fraction of ethanol (1) in the solvent mixtures is ur(x0B) = 0.005. a 0 xBis

Table 3. Mole Fraction Solubility of HH in the Binary 2-Propanol + Water Solvent Mixtures at Different Temperatures from 278.15 to 313.15 K at p = 0.1 MPaa,b,c,d,e x0B

103 xaexp

x0B

103 xAexp

0.000 0.099 0.198 0.299 0.399 0.499 0.600 0.700

38.58 25.04 16.42 9.57 5.14 2.19 0.78 0.29

0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700

39.34 25.36 16.56 9.60 5.17 2.20 0.78 0.29

0.000 0.099 0.198 0.298 0.399 0.499 0.600 0.700

40.97 28.70 18.54 11.01 5.86 2.71 0.95 0.28

0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700

41.83 29.12 18.71 11.07 5.88 2.73 0.95 0.28

0.000 0.098 0.198 0.298 0.399 0.499 0.600 0.700

43.24 31.51 20.85 13.21 6.75 3.19 1.07 0.34

0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700

44.19 32.02 21.07 13.31 6.78 3.20 1.07 0.34

0.000 0.098

46.20 34.15

0.000 0.100

47.30 34.74

103 xAcal(Apelbat)

103 xAcal(λh)

103 xacal(NRTL)

39.77 25.72 16.24 9.63 5.01 2.20 0.80 0.28

39.16 26.18 16.20 9.61 4.68 2.35 0.76 0.26

39.16 23.60 16.76 10.28 5.35 2.29 0.79 0.21

41.75 28.69 18.66 11.26 5.85 2.70 0.93 0.31

41.62 28.83 18.65 11.25 5.69 2.77 0.91 0.30

40.87 26.21 18.92 11.76 6.18 2.69 0.94 0.25

43.98 31.79 21.36 13.10 6.88 3.25 1.08 0.35

44.19 31.67 21.37 13.11 6.88 3.24 1.08 0.35

42.96 29.34 21.37 13.45 7.15 3.15 1.11 0.31

46.46 34.98

46.87 34.69

45.11 32.91

T = 278.15 K

T = 283.15 K

T = 288.15 K

T = 293.15 K

D



Article


103 xaexp

x0B

103 xAexp

0.198 0.298 0.398 0.499 0.600 0.700

23.78 15.13 7.84 3.87 1.27 0.40

0.200 0.300 0.400 0.500 0.600 0.700

24.07 15.28 7.84 3.87 1.27 0.40

0.000 0.098 0.197 0.297 0.398 0.499 0.600 0.700

48.27 37.56 26.60 17.38 9.19 4.50 1.48 0.47

0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700

49.47 38.28 26.96 17.56 9.27 4.51 1.48 0.47

0.000 0.098 0.197 0.297 0.398 0.499 0.599 0.700

50.43 40.51 31.70 19.95 12.21 5.20 1.73 0.49

0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700

51.74 41.35 32.21 20.18 12.30 5.21 1.73 0.49

0.000 0.098 0.196 0.297 0.397 0.499 0.599 0.700

52.79 44.15 35.06 22.33 13.35 5.81 1.98 0.55

0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700

54.22 45.14 35.69 22.54 13.51 5.82 1.98 0.55

0.000 0.098 0.196 0.296 0.397 0.498 0.599 0.700

58.69 47.27 38.40 26.18 16.21 6.57 2.42 0.68

0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700

60.46 48.41 39.15 26.43 16.40 6.59 2.42 0.68

103 xAcal(Apelbat)

103 xAcal(λh)

103 xacal(NRTL)

24.35 15.18 8.12 3.86 1.26 0.39

24.37 15.19 8.26 3.79 1.28 0.40

24.08 15.37 8.27 3.70 1.32 0.37

49.22 38.26 27.65 17.50 9.63 4.50 1.47 0.44

49.66 37.91 27.67 17.52 9.85 4.40 1.50 0.45

47.98 36.71 27.14 17.55 9.57 4.33 1.57 0.45

52.28 41.60 31.28 20.10 11.48 5.18 1.72 0.50

52.58 41.34 31.30 20.11 11.69 5.08 1.75 0.51

51.18 41.10 30.28 20.02 11.17 5.06 1.86 0.54

55.67 44.99 35.26 22.99 13.72 5.87 2.03 0.58

55.63 44.98 35.26 22.99 13.80 5.85 2.03 0.58

54.70 45.79 34.04 22.81 12.87 5.90 2.20 0.66

59.40 48.40 39.61 26.20 16.47 6.58 2.39 0.67

58.81 48.84 39.59 26.18 16.20 6.71 2.36 0.65

57.15 51.19 38.24 25.94 14.93 6.88 2.60 0.79

T = 293.15 K

T = 298.15 K

T = 303.15 K

T = 308.15 K

T = 313.15 K

the initial mole fraction of 2-propanol in the binary solvent mixture; ax0Bis the final mole fraction of ethanol in the binary solvent mixture; xexp A is the experimentally determined solubility based on thiamine hydrochloride in soultions; xexp A is the experimentally determined solubility based on HH cal exp cal in soultions; xcal A (Apelbat) and xA (λh) are the calculated solubility by Apelbat and λh based on xA , respectively. xA (NRTL) are the calculated c exp b solubility by NRTL equation based on xA . The standard uncertainty of temperature is uc(T) = 0.1 K. The relative standard uncertainty of the solubility measurement is ur(x) = 0.03. dThe relative uncertainty of pressure is ur(P) = 0.05. eThe relative standard uncertainty in mole fraction of 2-propanol (1) in the solvent mixtures is ur(x0B) = 0.005. a 0 xBis

known mass (0.1−0.3 mg) was added into the vessel, along with which the intensity of the laser decreased immediately. The intensity of laser increased gradually along with the dissolution of the particles of HH and reached the former constant. This process was repeated until the solid could not dissolve and the laser intensity kept constant. The mixture was considered as reaching phase equilibrium. Then the total consumption of the solute was recorded. Each measuring point was repeated at least three times. The saturated mole fraction solubility of HH (xA) was calculated from eq 1

xA =

m/M (m /M ) + (mB /MB) + (mW /MW )

(1)

where m, mB, mW are the masses of HH, corresponding organic solvent, and water, respectively. M, MB, MW represent the molecular mass of HH, corresponding organic solvent, and water, respectively. The initial mole fraction x0B of ethanol, 2-propanol or acetone in the binary solvents can be obtained from eq 2 xB0 = E

mB /MB (mB /MB) + (mW /MW )

(2) DOI: 10.1021/acs.jced.6b00613 J. Chem. Eng. Data XXXX, XXX, XXX−XXX


Article

Table 4. Mole Fraction Solubility of HH in the Binary Acetone + Water Solvent Mixtures at Different Temperatures from 278.15 to 313.15 K at p = 0.1 MPaa,b,c,d,e x0B

103 xaexp

x0B

103 xAexp

0.000 0.099 0.199 0.299 0.399 0.500 0.600

38.58 23.03 14.69 7.97 3.59 1.41 0.42

0.000 0.100 0.200 0.300 0.400 0.500 0.600

39.34 23.30 14.80 8.03 3.60 1.42 0.42

0.000 0.099 0.198 0.299 0.399 0.500 0.600

40.97 25.80 16.54 9.17 3.97 1.78 0.45

0.000 0.100 0.200 0.300 0.400 0.500 0.600

41.83 26.14 16.68 9.07 4.02 1.78 0.46

0.000 0.099 0.198 0.298 0.399 0.499 0.600

43.24 28.87 18.63 10.73 4.67 2.01 0.50

0.000 0.100 0.200 0.300 0.400 0.500 0.600

44.19 29.30 18.81 10.73 4.73 2.01 0.50

0.000 0.098 0.198 0.298 0.399 0.499 0.600

46.20 32.10 20.25 11.31 5.45 2.32 0.58

0.000 0.100 0.200 0.300 0.400 0.500 0.600

47.30 32.62 20.46 11.35 5.45 2.32 0.58

0.000 0.098 0.198 0.298 0.399 0.499 0.600

48.27 34.93 23.78 12.59 6.55 2.72 0.63

0.000 0.100 0.200 0.300 0.400 0.500 0.600

49.47 35.56 24.06 13.93 6.59 2.73 0.63

0.000 0.098 0.197 0.298 0.398 0.499 0.600

50.43 39.79 26.23 15.43 7.74 3.01 0.69

0.000 0.100 0.200 0.300 0.400 0.500 0.600

51.74 40.60 26.58 15.63 7.72 3.02 0.69

0.000 0.098 0.197 0.297 0.398 0.499 0.600

52.79 43.72 31.22 17.43 8.48 3.35 0.78

0.000 0.100 0.200 0.300 0.400 0.500 0.600

54.22 44.69 31.71 17.53 8.70 3.36 0.78

0.000 0.097 0.196

58.69 47.76 34.79

0.000 0.100 0.200

60.46 48.93 35.40

103 xAcal(Apelbat)

103 xAcal(λh)

103 xacal(NRTL)

39.77 23.30 14.86 7.95 3.46 1.43 0.42

39.16 23.21 14.11 7.90 3.46 1.54 0.40

39.16 22.67 14.56 8.01 3.69 1.39 0.40

41.75 26.12 16.56 9.14 4.09 1.73 0.46

41.62 26.09 16.27 9.12 4.09 1.77 0.45

40.87 25.38 16.46 9.12 4.20 1.60 0.46

43.98 29.20 18.58 10.48 4.80 2.04 0.51

44.19 29.22 18.69 10.48 4.80 2.02 0.51

42.96 28.38 18.60 10.42 4.81 1.84 0.53

46.46 32.56 20.96 11.97 5.61 2.36 0.56

46.87 32.61 21.36 12.00 5.61 2.30 0.57

45.11 31.73 21.00 11.80 5.52 2.13 0.62

49.22 36.21 23.77 13.64 6.53 2.69 0.63

49.66 36.27 24.30 13.68 6.53 2.61 0.64

47.98 35.50 23.74 13.44 6.36 2.44 0.72

52.28 40.18 27.09 15.49 7.56 3.02 0.70

52.58 40.23 27.55 15.53 7.56 2.95 0.71

51.18 39.43 26.79 15.43 7.33 2.80 0.83

55.67 44.47 31.02 17.56 8.71 3.34 0.79

55.63 44.47 31.11 17.56 8.71 3.32 0.79

54.70 43.91 30.19 17.59 8.37 3.22 0.97

59.40 49.11 35.67

58.81 49.03 34.99

57.15 48.86 33.96

T = 278.15 K

T = 283.15 K

T = 288.15 K

T = 293.15 K

T = 298.15 K

T = 303.15 K

T = 308.15 K

T = 313.15 K

F



Article


103 xaexp

x0B

103 xAexp

0.297 0.398 0.499 0.600

19.70 9.79 3.61 0.90

0.300 0.400 0.500 0.600

19.80 9.95 3.62 0.90

103 xAcal(Apelbat)

103 xAcal(λh)

103 xacal(NRTL)

19.80 10.00 3.73 0.88

20.04 9.63 3.70 1.12

T = 313.15 K 19.85 10.00 3.63 0.89

the initial mole fraction of acetone in the binary solvent mixture; x0Bis the final mole fraction of ethanol in the binary solvent mixture; xexp A is the experimentally determined solubility based on thiamine hydrochloride in soultions; xexp A is the experimentally determined solubility based on HH in cal exp cal soultions; xcal A (Apelbat) and xA (λh) are the calculated solubility by Apelbat and λh based on xA , respectively. xA (NRTL) are the calculated b c solubility by NRTL equation based on xexp A . The standard uncertainty of temperature is uc(T) = 0.1 K. The relative standard uncertainty of the solubility measurement is ur(x) = 0.03. dThe relative uncertainty of pressure is ur(P) = 0.05. eThe relative standard uncertainty in mole fraction of acetone (1) in the solvent mixtures is ur(x0B) = 0.005. a 0 xBis

Figure 4. Mole fraction solubility (xA) of HH versus mole fractions of ethanol (x0B) in water (W) + ethanol (B) binary solvent mixtures at different temperatures.

3. THERMODYNAMIC MODELS 3.1. Modified Apelbat Equation. The modified Apelblat equation14,15 was used to show the relationship between the mole fraction of HH and temperature ln xA = A +

B + C ln(T /K) T /K

ln xi =

(5)

where ΔfusH and Tmelt stand for the enthalpy of fusion and melting temperature of solute. γi is the activity coefficient of solute in the saturated solution, which can be calculated by NRTL model

(3)

where xA is the mole fraction solubility, T is the absolute temperature, A, B, and C are the empirical constants. The value of C denotes the effect of temperature on the fusion enthalpy. The values of A and B refer to the variations in the solution activity coefficient. 3.2. λh Model. The λh model equation which was originally developed by Buchowski et al.16 expressed the nonideality and the enthalpy of solution. The equation has two parameters λ and h. It can be shown as eq 4 ⎛1 ⎛ 1 − x⎞ 1 ⎞ ln⎜1 + λ ⎟ = λh⎜ − ⎟ xA ⎠ Tm ⎠ ⎝T ⎝

ΔfusH ⎛ 1 1⎞ − ⎟ − ln γi ⎜ R ⎝ Tmelt T⎠

ln γi =

+

+

(Gjixj + Gkixk)(τjiGjixj + τkiGkixk) (xi + xjGji + xkGki)2 [τijGijxj 2 + GijGkjxjxk(τij − τkj)] xj + xiGij + xkGkj 2

[τijGik xk 2 + Gik Gjk xjxk(τik − τjk)] (xk + xiGik + xjGjk )2

(6)

where Gij, Gik, Gji, Gjk, Gki, Gkj, τij, τik, τji, τjk, τki, and τkj are parameters of this model. The definition of these terms can be expressed as

(4)

where xA is the mole fraction solubility of the solute in the solution. Tm is the melting temperature of the solute. T stands for the absolute temperature. The parameters of λ and h are determined by correlation of the solubility data. 3.3. NRTL Model. According to the solid−liquid phase equilibrium theory and the solute−solvent interactions, the local composition equation17 can be simplified and expressed by eq 5

Gij = exp( −αijτij) τij =

(gij − gjj) RT

=

(7)

Δgij RT

(8)

where Δgij represents the Gibbs energy of intermolecular interaction, which are independent of the composition and G



Article

Figure 5. Mole fraction solubility (xA) of HH versus mole fractions of 2-propanol (x0B) in water (W) + 2-propanol (B) binary solvent mixtures at different temperatures.

Figure 6. Mole fraction solubility (xA) of HH versus mole fractions of acetone (x0B) in water (W) + acetone (B) binary solvent mixtures at different temperatures.

temperature. αij is an adjustable empirical constant between 0 and 1. It is a criterion of the nonrandomness of the solution. In order to evaluate the applicability and correlate accuracy of the three models above, the average relative deviation (ARD %) was also shown to assess the accuracy of different models.18 They were calculated according to eq 9 ARD% = exp

100 N

N2

∑ i=1

(xwater = 0.1, 0.5, 0.9)) at fixed temperature (T = (278.15, 298.15, 313.15) K) after a 24 h of stirring. As shown in Figure 2, we take the PXRD pattern of the sediments in different ratios of binary solvents (water + ethanol) at temperature T = 313.15 K as an example. All the PXRD pattern of HH samples have the same characteristic peaks of HH, comparing with the PXRD pattern of HH from the literature.10 Therefore, it can be confirmed that the solute used in this study is thiamine hydrochloride hemihydrate (HH) and there is no crystal phase transformation during the process of solubility determination in the solution. 4.1.2. TGA/DSC. In order to ensure the form further, we also use the TGA/DSC to characterize the solid of HH. The results showed that the curves were the same and we take one as example. As shown in Figure 3 (T = 313.15 K, xwater = 0.1), there was negligible weight loss up to 120 °C. In the temperature range of 120−200 °C, the observed weight loss of ∼1% is substantially lower than the stoichiometric water content of 2.6% (w/w) in the HH. The shoulder on the edge of the DSC endotherm indicated that there were overlapping thermal events. This showed that the dehydration and decomposition occurred at the same time at higher temperatures (T > 120 °C). All these were consistent with

xA, i exp − xA, i cal xA, i exp

(9)

cal

where xA,i and xA,i represent the experimental and calculated solubility data, respectively, and N is the number of experimental points.

4. RESULTS AND DISCUSSION 4.1. Identification and Characterization of HH. 4.1.1. X-ray Powder Diffraction. The purchased material as well as the prepared powder was tested by the X-ray powder diffraction (PXRD) pattern and the results were turn out to be HH (Figure 2). We also characterized the excess solid in different solvents, the ratios of which were (water + 2-propanol/ethanol/acetone H



Article

Table 5. Relative Dielectric Constant, εr, of HH at p = 0.1 MPa and the Relative Parameters in Different Solvent Mixtures εr x0B

T/K 278.15 283.15 288.15 293.15 298.15 303.15 308.15 313.15

278.15 283.15 288.15 293.15 298.15 303.15 308.15 313.15

278.15 283.15 288.15 293.15 298.15 303.15 308.15 313.15

0.099 77.98 0.098 76.25 0.098 74.55 0.098 72.89 0.098 71.27 0.098 69.67 0.098 68.11 0.097 66.60

0.198 70.64 0.198 69.06 0.197 67.51 0.197 66.02 0.197 64.56 0.197 63.12 0.196 61.72 0.196 60.36

0.298 63.73 0.298 62.30 0.297 60.90 0.297 59.55 0.296 58.23 0.296 56.93 0.296 55.67 0.295 54.47

0.398 57.27 0.398 55.97 0.398 54.70 0.397 53.47 0.397 52.29 0.397 51.12 0.396 49.99 0.395 48.92

0.099 76.97 0.099 75.19 0.098 73.44 0.098 71.73 0.098 70.06 0.098 68.42 0.098 66.81 0.098 65.24

0.198 68.72 0.198 67.06 0.198 65.43 0.198 63.84 0.197 62.28 0.197 60.77 0.196 59.27 0.196 57.81

0.299 61.05 0.298 59.50 0.298 57.98 0.298 56.49 0.297 55.04 0.297 53.62 0.297 52.22 0.296 50.88

0.399 53.96 0.399 52.51 0.399 51.08 0.398 49.69 0.398 48.34 0.398 47.03 0.397 45.73 0.397 44.47

0.099 77.01 0.099 75.29 0.099 73.60 0.098 71.95 0.098 70.33 0.098 68.75 0.098 67.20 0.097 65.69

0.199 68.81 0.198 67.25 0.198 65.73 0.198 64.23 0.198 62.78 0.197 61.35 0.197 59.98 0.196 58.62

0.299 61.18 0.299 59.76 0.298 58.39 0.298 57.03 0.298 55.73 0.298 54.44 0.297 53.19 0.297 51.98

0.399 54.11 0.399 52.83 0.399 51.59 0.399 50.37 0.399 49.19 0.398 48.04 0.398 46.92 0.398 45.83

0.499 51.26 0.499 50.06 0.498 48.91 0.498 47.81 0.498 46.74 0.498 45.68 0.497 44.68 0.496 43.72 2-Propanol + Water 0.499 47.43 0.499 46.08 0.499 44.76 0.499 43.47 0.499 42.21 0.499 40.97 0.499 39.76 0.498 38.58 Acetone + Water 0.500 47.62 0.500 46.48 0.499 45.36 0.499 44.27 0.499 43.20 0.499 42.17 0.499 41.16 0.499 40.18

the literature.10 Besides, this phenomenon showed that HH did not have a real melting point and the melting temperature Tm of HH could not be obtained by this conventional calorimetric method. It has been known that the melting point of compounds can be estimated by using group contribution method according to the literatures.19,20 Then a combined method of additive group contribution and nonadditive molecular parameters21 was used to estimate the melting points of HH. The method was

k

Ex kJ·mol−1

0.599 45.67 0.599 44.60 0.599 43.55 0.599 42.55 0.598 41.59 0.598 40.65 0.598 39.75 0.598 38.88

0.700 40.52 0.700 39.55 0.699 38.61 0.699 37.71 0.699 36.85 0.699 36.01 0.699 35.21 0.699 34.44

0.800 35.77 0.800 34.90 0.800 34.06 0.800 33.26 0.800 32.49 0.800 31.75 0.800 31.04 0.799 30.36

0.81

2.18

0.89

2.12

0.93

2.04

1.00

1.94

1.00

1.85

1.02

1.79

1.02

1.70

1.15

1.65

0.600 41.46 0.600 40.21 0.600 38.99 0.600 37.79 0.600 36.62 0.599 35.48 0.599 34.36 0.599 33.27

0.700 36.03 0.700 34.88 0.700 33.75 0.700 32.65 0.700 31.57 0.700 30.52 0.700 29.49 0.700 28.49

1.39

2.55

1.47

2.44

1.49

2.33

1.43

2.19

1.38

2.06

1.47

1.98

1.43

1.87

1.36

1.95

2.78

3.02

2.85

2.90

3.02

2.81

2.94

2.68

3.04

2.58

3.30

2.50

3.46

2.42

3.70

2.34

0.600 41.68 0.600 40.65 0.600 39.65 0.600 38.67 0.600 37.73 0.600 36.80 0.600 35.91 0.600 35.04

proved with relatively high accuracy by estimating the normal melting points of 1215 organic compounds. The equation of this method can be expressed as follows

Tm =

ΔHm ΔSm

ΔHm = I

∑ nimi

(10) (11) DOI: 10.1021/acs.jced.6b00613 J. Chem. Eng. Data XXXX, XXX, XXX−XXX


Article

Figure 7. Correlation of ln x versus εmix in water (W) + ethanol (B) binary solvent mixtures at different temperatures: ■, T = 278.15 K; red ●, T = 283.15 K; blue ▲, T = 288.15 K; aqua ▼, T = 293.15 K; navy ◆, T = 298.15 K; fuschia ◀, T = 303.15 K; green ▶, T = 308.15 K; brown ⬟, T = 313.15 K.

Figure 9. Correlation of ln x versus εmix in water (W) + acetone (B) binary solvent mixtures at different temperatures: ■, T = 278.15 K; red ●, T = 283.15 K; blue ▲, T = 288.15 K; aqua ▼, T = 293.15 K; navy ◆, T = 298.15 K; fuschia ◀, T = 303.15 K; green ▶, T = 308.15 K; brown ⬟, T = 313.15 K.

(278.15−313.15) K were drawn in Figures 4−6. From Figures 4−6, it can be clearly seen that the solubility of HH is a function of temperature and increases with increasing temperature in all studied binary solvent mixtures at constant solvent compositions. Besides, at a certain constant temperature, the solubility of HH decreased apparently with the increasing of the initial mole fraction of the organic solvents (ethanol/ acetone/2-propanol). It can also be concluded that the solubility of HH in mixed solvents followed the order of (ethanol + water) > (2-propanol + water) > (acetone + water), which indicated that the solubility increased with an increase of the polarity of the mixture solvents. This result shows that the three organic solvents + water mixture is the suitable cosolvents for the recrystallization of HH. These phenomena may be due to the polarity of the different solvents, hydrogen bonding interaction, ionization of the solute, and so on.22 4.3. Correlation of the Solubility Data of HH versus Dielectric Constant. Referring to the molecular structure of thiamine hydrochloride (Figure 1) and the physicochemical properties of different solvents, the polarity was thought to be one factor to determine the solubility order, which was in according with the empirical rule of “like dissolves like”. If the solvent molecules and the solute molecules have the similar polarity, it needs smaller energy barrier for the solute molecules to combine with solvent molecules. The order of solvents’ polarity was as follows: water > ethanol >2-propanol > acetone. From above, we can only get the qualitative conclusion that the solubility of HH rises as the polarity of the binary solvents increasing. The empirical polarities (ENT ), dipole moments (μ), and dielectric constants (ε) of the solubility behavior of solute in the selected solvents are usually used as the criterions of solvent polarity. The relative dielectric constant (εr) is a good index of polarity among them. We used a modified form of Arrhenius equation to quantitatively show the relationship between the solubility and the dielectric constant of the binary solvents in this work. According to the literature,23 the dielectric constants of mixture solvents on composition of solvents were calculated by the sum law of square roots

Figure 8. Correlation of ln x versus εmix in water (W) + 2-propanol (B) binary solvent mixtures at different temperatures: ■, T = 278.15 K; red ●, T = 283.15 K; blue ▲, T = 288.15 K; aqua ▼, T = 293.15 K; navy ◆, T = 298.15 K; fuschia ◀, T = 303.15 K; green ▶, T = 308.15 K; brown ⬟, T = 313.15 K.

ΔSm = C − R ln σ + RnΦ

(12)

where nimi is the contribution of group i to the enthalpy of melting. σ represents the number of positions into which a molecule can be rotated that are identical with a reference position and Φ indicates the molecular flexibility. The melting point of HH and the fusion enthalpy ΔfusH calculated from the above multilevel scheme were 518.15 K and 30.13 kJ·mol−1, respectively. 4.2. Experimental Solubility. Experimental mole fraction solubility data of HH in binary (ethanol + water, 2-propanol + water, and acetone + water) solvent mixtures are listed in Tables 2, 3, and 4. The average relative deviation (ARD%) were also shown in Tables S1−3 to assess the accuracy of different models, which all gave satisfactory correlation results. Besides, to show the experimental values clearly, the plots of the solubility data of HH in these binary solvents at the temperature range of J



Article

Table 6. Mixing Thermodynamic Properties of HH in the Binary Ethanol + Water Solvent Mixtures from 278.15 to 313.15 K at p = 0.1 MPaa

a

x0B

ΔmixG kJ·mol−1

0.099 0.198 0.298 0.398 0.499 0.599 0.700 0.800

−1.092 −1.222 −1.262 −1.236 −1.143 −0.989 −0.790 −0.548

0.098 0.198 0.298 0.398 0.499 0.599 0.700 0.800

−1.135 −1.277 −1.306 −1.268 −1.160 −1.005 −0.800 −0.555

0.098 0.197 0.297 0.398 0.498 0.599 0.699 0.800

−1.180 −1.312 −1.347 −1.300 −1.184 −1.020 −0.811 −0.563

0.098 0.197 0.297 0.397 0.498 0.599 0.699 0.800

−1.272 −1.399 −1.416 −1.350 −1.219 −1.040 −0.825 −0.573

ΔmixS J·mol−1·K−1 T = 278.15 K 0.137 1.190 2.048 2.496 2.659 2.588 2.313 1.758 T = 283.15 K 0.106 0.990 1.876 2.373 2.596 2.538 2.294 1.732 T = 288.15 K 0.090 0.870 1.723 2.252 2.508 2.490 2.275 1.724 T = 293.15 K 0.077 0.564 1.464 2.064 2.381 2.426 2.248 1.710

ΔmixH kJ·mol−1

x0B

ΔmixG kJ·mol−1

−1.054 −0.891 −0.692 −0.542 −0.403 −0.269 −0.147 −0.059

0.098 0.197 0.296 0.397 0.498 0.598 0.699 0.800

−1.335 −1.456 −1.473 −1.395 −1.252 −1.064 −0.839 −0.582

−1.105 −0.997 −0.775 −0.596 −0.425 −0.286 −0.151 −0.065

0.098 0.196 0.296 0.396 0.497 0.598 0.699 0.800

−1.362 −1.468 −1.489 −1.414 −1.267 −1.074 −0.848 −0.590

−1.154 −1.061 −0.850 −0.651 −0.461 −0.303 −0.155 −0.066

0.098 0.196 0.296 0.396 0.497 0.598 0.699 0.800

−1.413 −1.508 −1.533 −1.448 −1.303 −1.093 −0.862 −0.600

−1.249 −1.233 −0.987 −0.745 −0.521 −0.329 −0.165 −0.071

0.097 0.196 0.295 0.395 0.496 0.598 0.699 0.799

−1.477 −1.594 −1.591 −1.503 −1.348 −1.116 −0.879 −0.608

ΔmixS J·mol−1·K−1 T = 298.15 K 0.051 0.371 1.254 1.892 2.263 2.355 2.222 1.682 T = 303.15 K 0.038 0.336 1.197 1.823 2.211 2.327 2.209 1.673 T = 308.15 K 0.023 0.207 1.041 1.698 2.083 2.271 2.186 1.677 T = 313.15 K 0.012 0.057 0.833 1.499 1.924 2.205 2.154 1.667

ΔmixH kJ·mol−1 −1.319 −1.345 −1.099 −0.831 −0.577 −0.361 −0.176 −0.080 −1.351 −1.366 −1.127 −0.861 −0.597 −0.369 −0.179 −0.083 −1.406 −1.444 −1.212 −0.925 −0.661 −0.393 −0.189 −0.083 −1.473 −1.577 −1.331 −1.033 −0.745 −0.425 −0.205 −0.086

The combined expanded uncertainties are uc(ΔmixS) = 0.065ΔmixS, uc(ΔmixG) = 0.044ΔmixG (0.95 level of confidence).

εm1/3 =

∑ φεi i1/3 i

⎛ Ex ⎞ xA = k exp⎜ − ⎟ ⎝ Rεmix (T ) ⎠

(13)

Akerlof has already reported that the logarithm of dielectric constant is a linear function of the absolute temperature. The dependence of relative dielectric constant on temperature can be reflected by eq 1424 εr(T ) = a + bT + cT 2 + dT 3

(15)

where xA is the solubility of solute, and R is the gas constant. εmix(T), a function of temperature and composition of solvents, stands for the dielectric constants of binary solvents at a certain temperature. Ex represents the dissolution energy barrier. When the value of M is greater, it is more difficult for the solids to dissolve in binary solvents. The values of Ex and k can be calculated from the slope and the interception of the plot, which are listed in Table 5. The results indicated that this model could well describe the relationship of the solubility and dielectric constant. The solubility increased with increasing dielectric constant and the content of water in binary solvents, which was in accordance with the rule of “like dissolving like”. 4.4. Solution Mixing Thermodynamics. For real solutions, it is necessary to study the mixing thermodynamic properties of the solute in different binary solvent mixtures. When the activity coefficients are taken into consideration, the thermodynamic properties such as the mixing enthalpy (ΔmixH), the mixing Gibbs energy (ΔmixG) and the mixing

(14)

where εi is the relative dielectric constant of pure component i and φi represents the volume fraction of component i in the solvent mixtures in absence of solute. The parameter a, b, c, and d available from the literature are empirical coefficients. The dielectric constants of the binary solvent mixtures could be calculated through the eq 13−14 and the results were listed in Table 5. The plots of ln xA with −1/εmix were drawn in Figures 7−9. According to the Figures, the linear fitting of ln xA versus −1/εmix was good for HH, which could be described by a model outwardly like the Arrhenius eq eq 15 K



Article

Table 7. Mixing Thermodynamic Properties of HH in the Binary 2-Propanol + Water Solvent Mixtures from 278.15 to 313.15 K, p = 0.1 MPaa

a

x0B

ΔmixG kJ·mol−1

0.099 0.198 0.298 0.399 0.499 0.600 0.700

−1.373 −1.724 −1.974 −2.144 −2.230 −2.222 −2.087

0.099 0.198 0.298 0.399 0.499 0.600 0.700

−1.442 −1.775 −2.009 −2.167 −2.247 −2.231 −2.089

0.098 0.198 0.298 0.399 0.499 0.600 0.700

−1.496 −1.823 −2.055 −2.192 −2.264 −2.239 −2.093

0.098 0.198 0.298 0.398 0.499 0.600 0.700

−1.546 −1.880 −2.098 −2.221 −2.284 −2.249 −2.098

ΔmixS J·mol−1·K−1 T = 278.15 K 2.039 2.370 2.460 2.408 2.234 1.909 1.399 T = 283.15 K 2.112 2.430 2.521 2.481 2.322 2.018 1.526 T = 288.15 K 2.180 2.492 2.580 2.553 2.408 2.124 1.649 T = 293.15 K 2.249 2.557 2.643 2.622 2.491 2.225 1.765

ΔmixH kJ·mol−1

x0B

ΔmixG kJ·mol−1

−0.806 −1.065 −1.289 −1.474 −1.608 −1.691 −1.698

0.098 0.197 0.297 0.398 0.499 0.600 0.700

−1.609 −1.935 −2.144 −2.254 −2.305 −2.261 −2.104

−0.844 −1.087 −1.295 −1.464 −1.590 −1.659 −1.657

0.098 0.197 0.297 0.398 0.499 0.599 0.700

−1.663 −2.022 −2.194 −2.309 −2.326 −2.273 −2.110

−0.868 −1.105 −1.312 −1.457 −1.570 −1.627 −1.618

0.098 0.196 0.297 0.397 0.499 0.599 0.700

−1.727 −2.083 −2.241 −2.338 −2.346 −2.286 −2.116

−0.887 −1.131 −1.323 −1.453 −1.554 −1.597 −1.581

0.098 0.196 0.296 0.397 0.498 0.599 0.700

−1.782 −2.142 −2.308 −2.390 −2.369 −2.302 −2.125

ΔmixS J·mol−1·K−1 T = 298.15 K 2.324 2.623 2.706 2.690 2.573 2.323 1.875 T = 303.15 K 2.397 2.697 2.770 2.747 2.652 2.417 1.982 T = 308.15 K 2.475 2.770 2.836 2.819 2.732 2.508 2.084 T = 313.15 K 2.550 2.842 2.901 2.879 2.809 2.595 2.181

ΔmixH kJ·mol−1 −0.916 −1.153 −1.337 −1.451 −1.537 −1.568 −1.545 −0.936 −1.205 −1.355 −1.477 −1.522 −1.540 −1.509 −0.964 −1.229 −1.367 −1.470 −1.504 −1.513 −1.474 −0.984 −1.252 −1.399 −1.489 −1.489 −1.489 −1.442

The combined expanded uncertainties are uc(ΔmixS) = 0.065ΔmixS, uc(ΔmixG) = 0.044ΔmixG (0.95 level of confidence).

entropy (ΔmixS) were calculated by the following equations25 based on the NRTL model Δmix G = GE + Δmix Gid

(16)

Δmix H = HE + Δmix H id

(17)

Then, the mixing enthalpy (ΔmixH), the mixing Gibbs energy (ΔmixG), and the mixing entropy (ΔmixS) can be calculated by the following equations:26 n

Δmix S = S E + Δmix S id

GE = RT ∑ xi ln γi i

(18) n ⎛ ∂lnγi ⎞ HE = −RT 2 ∑ xi⎜ ⎟ ⎝ ∂T ⎠ p , x i

where G , S , and H stand for the excess properties and ΔmixGid, ΔmixSid, and ΔmixHid are the mixing properties of ideal systems. The mixing thermodynamic properties of the ideal solution can be obtained by the following equations:25 E

E

E

n

Δmix Gid = RT ∑ xi ln xi i

Δmix H id = 0

SE = (19)

n i

HE − GE T

(23)

(24)

where xi and γi represent the mole fraction and activity coefficient of component i in real solution, respectively. n = 2 means binary solution and n = 3 means ternary solution. The calculated mixing thermodynamic properties of HH were given in Tables 6 to 8. As shown in these tables, it can conclude that the values of ΔmixG are all negative, which indicate that the mixing of HH in all studied solvents is a spontaneous and favorable process. The negative values of ΔmixH reflect that the mixing process is exothermic.

(20)

Δmix S id = −R ∑ xi ln xi

(22)

(21)

where xi and γi stand for the mole fraction and activity coefficient of component i in real solution, respectively. For the solution with pure solvents, n = 2. For the solution with binary solvents, n = 3. L



Article

5. CONCLUSION The solubility of HH in water + ethanol/2-propanol/acetone binary solvent mixtures was experimentally determined at temperatures ranging from 278.15 to 313.15 K under atmospheric pressure by a laser monitoring observation method. It was obvious that the solubility of HH in all examined binary solvents increased with the rising of temperature and decreased with the addition of organic solvents (ethanol, acetone, 2-propanol). Besides, the solubility was in the order of (ethanol + water) > (2-propanol + water) > (acetone + water). The modified Apelblat equation, the λh equation, and NRTL equation were used to correlate the solubility in binary solvents system to correlate the measured solubility data respectively, all of which could give satisfactory correlation results. On the basis of the NRTL equation, thermodynamic parameters including the mixing enthalpy, entropy, and Gibbs energy were obtained. It was found that the mixing process of HH was exothermic and spontaneous. On the other hand, the phenomenon that solubility of HH increased with the polarity of the binary solvents was quantitatively explained by the function outwardly Arrhenius equation. In general, the experimental results and the resulting parameters can be used to optimize the purification process of thiamine hydrochloride.

Table 8. Mixing Thermodynamic Properties of HH in the Binary Acetone + Water Solvent Mixtures from 278.15 to 313.15 K, p = 0.1 MPaa x0B

ΔmixG kJ·mol−1

0.099 0.199 0.299 0.399 0.500 0.600

−1.124 −1.273 −1.310 −1.285 −1.212 −1.086

0.099 0.198 0.299 0.399 0.500 0.600

−1.177 −1.313 −1.340 −1.301 −1.227 −1.094

0.099 0.198 0.298 0.399 0.499 0.600

−1.235 −1.356 −1.375 −1.322 −1.240 −1.104

0.098 0.198 0.298 0.399 0.499 0.600

−1.294 −1.391 −1.395 −1.345 −1.258 −1.114

0.098 0.198 0.298 0.399 0.499 0.600

−1.347 −1.456 −1.425 −1.373 −1.271 −1.125

0.098 0.197 0.298 0.398 0.499 0.600

−1.430 −1.504 −1.480 −1.402 −1.286 −1.136

0.098 0.197 0.297 0.398 0.499 0.600

−1.497 −1.588 −1.521 −1.424 −1.302 −1.148

0.097 0.196 0.297 0.398 0.499 0.600

−1.564 −1.650 −1.565 −1.455 −1.318 −1.161

ΔmixS J·mol−1·K−1 T = 278.15 K 1.715 2.001 2.067 2.039 1.966 1.886 T = 283.15 K 1.764 2.043 2.112 2.101 2.038 1.976 T = 288.15 K 1.816 2.087 2.155 2.158 2.112 2.064 T = 293.15 K 1.871 2.136 2.210 2.213 2.180 2.149 T = 298.15 K 1.929 2.179 2.260 2.266 2.253 2.231 T = 303.15 K 1.989 2.230 2.298 2.318 2.323 2.311 T = 308.15 K 2.053 2.274 2.347 2.377 2.392 2.388 T = 313.15 K 2.119 2.328 2.396 2.430 2.460 2.463

ΔmixH kJ·mol−1 −0.647 −0.716 −0.735 −0.718 −0.665 −0.561 −0.678 −0.734 −0.742 −0.706 −0.650 −0.535 −0.712 −0.755 −0.754 −0.700 −0.631 −0.509

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ASSOCIATED CONTENT

S Supporting Information *

−0.746 −0.765 −0.747 −0.696 −0.618 −0.484

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jced.6b00613.

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Calculated parameters for different models. (PDF)

AUTHOR INFORMATION

Corresponding Author

−0.772 −0.807 −0.751 −0.697 −0.599 −0.459

*E-mail: [email protected]. Tel.: 86-22-27405754. Fax: +86-22-27374971. Funding

We are grateful for the financial support of the National Natural Science Foundation of China (No. NNSFC 21176173), and the Major National Scientific Instrument Development Project (No.21527812).

−0.827 −0.828 −0.783 −0.699 −0.582 −0.435

Notes

The authors declare no competing financial interest.

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REFERENCES

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−0.864 −0.888 −0.798 −0.692 −0.565 −0.412 −0.901 −0.921 −0.815 −0.694 −0.548 −0.390

a

The combined expanded uncertainties are uc(ΔmixS) = 0.065ΔmixS, uc(ΔmixG) = 0.044ΔmixG (0.95 level of confidence). M



Article

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Measurement of Solubility of Thiamine Hydrochloride Hemihydrate in

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