# Investigation of [BMIM]FeCl4 ionic liquid as an additive for carbon capture using gas hydrates with seawater

Angsar Serikkali, Jérôme Douzet, Jean-Michel Herri, Baptiste Bouillot

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Angsar Serikkali, Jérôme Douzet, Jean-Michel Herri, Baptiste Bouillot. Investigation of [BMIM]FeCl4 ionic liquid as an additive for carbon capture using gas hydrates with seawater. Journal of Molecular Liquids, 2025, 432, pp.127728. 10.1016/j.molliq.2025.127728. emse-05076915

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# Investigation of [BMIM]FeCl₄ ionic liquid as an additive for carbon capture using gas hydrates with seawater

Angsar Serikkali, Jérôme Douzet, Jean-Michel Herri, Baptiste Bouillot*

Mines Saint-Etienne, Univ Lyon, CNRS, UMR 5307 LGF, Centre SPIN, F-42023 Saint-Etienne, France

## ARTICLE INFO

**Keywords:**

Ionic liquids

Gas hydrates

Carbon capture

Thermodynamics

Kinetics

## ABSTRACT

Carbon capture through gas hydrate formation represents a highly promising avenue for mitigating greenhouse gas emissions. The unique structure of gas hydrates allows for the efficient trapping of gases like CO₂, potentially offering a robust solution for carbon sequestration. However, the practical implementation of this technology faces several challenges, primarily related to the kinetics of hydrate formation and the stability of hydrates under varying conditions. The use of promoters has shown potential in overcoming some of these kinetic barriers. A few years ago, iron-based ionic liquids were studied as kinetic promoters for gas hydrates. Since hydrate formation kinetics pose a well-known challenge for developing hydrate-based technologies, this study aims to evaluate the effectiveness of [BMIM]FeCl₄ ionic liquid for carbon capture from seawater. The research is divided into three stages: analyzing the influence of NaCl concentration on the liquid-liquid equilibrium of brine and ionic liquids; examining the thermodynamic equilibrium of CO₂ hydrates in the presence of seawater and ionic liquids; and investigating the kinetics of hydrate formation. The first stage produced a two-phase ternary diagram relevant to expected industrial conditions, and the kinetic constants for gas-to-liquid and liquid-to-hydrate mass transfer were estimated. The results demonstrated a thermodynamic inhibition effect for CO₂ hydrates. However, from a kinetic perspective, no significant improvement was observed. Consequently, [BMIM]FeCl₄ did not prove to be an effective overall promoter.

## 1. Introduction

The substantial increase in the global human population and economic activity has significantly influenced atmospheric carbon levels, leading to the release of large amounts of carbon dioxide (CO₂) into the atmosphere. This phenomenon is primarily driven by high energy consumption, the carbon intensity of energy systems, and limited CO₂ absorption capacity [1].

One of the most promising approaches to mitigating greenhouse gas emissions involves capturing and sequestering CO₂ and other gases, particularly from feed and flue gases [2], using carbon capture and storage (CCS) technology. This strategy is a key focus of the Kyoto Protocol [3] due to its effectiveness in swiftly reducing emissions from fossil fuel combustion [4].

The potential of hydrates for carbon dioxide capture hinges on overcoming several thermodynamic and kinetic challenges during their synthesis [5]. One of the primary obstacles is the sluggish initiation of hydrate nucleation, which involves the formation of the initial stable crystal capable of subsequent growth [6–9]. The induction time required

for hydrate nucleation can vary significantly, ranging from hours to days, particularly in the absence of external promotion techniques, despite nucleation being primarily influenced by thermodynamic conditions. This issue could be overcome with the consideration of a continuous process. Other significant challenges related to hydrate formation include sluggish growth rates and low conversion rates from gas to hydrate [10].

Recent advancements have aimed to mitigate the challenge of unpredictable and prolonged induction periods in hydrate formation. Surfactants, ionic liquids, and proteins are recognized as effective kinetic promoters capable of enhancing the nucleation rate of hydrates [11–17].

Ionic liquids are being investigated as potential replacements for traditional inhibitors of gas hydrates. Their ability to establish hydrogen bonds makes them highly effective in this capacity. Research by Xiao and Adidharma [18] and Khan et al. [19] underscores the necessity for ionic liquids to exhibit hydrophilic characteristics to overcome the thermodynamic barriers associated with hydrates. Hydrophobic variants, if present, would remain segregated as a distinct layer and fail to

<footnote>* Corresponding author.</footnote>

<footnote>E-mail address: bouillot@emse.fr (B. Bouillot).</footnote>
engage in hydrogen bonding with water molecules. The inclusion of specific functional groups, such as hydroxyl (OH⁻) and oxygen (O²⁻) within ionic liquids, plays a pivotal role in disrupting intermolecular interactions with water molecules, thereby impeding the formation of hydrate nuclei. Additionally, ionic liquids possess versatility, serving as effective kinetic inhibitors of hydrates and demonstrating efficacy in minimal quantities to mitigate hydrate formation in scenarios involving CH₄, CO₂, and mixed gases, as evidenced by further investigations conducted by Kim et al. [20]. Long et al. [21] conducted an investigation into the phase equilibrium of methane in the presence of imidazolium-based ionic liquids, specifically examining 1-ethyl-3-methylimidazolium nitrate ([EMIM]NO₃) and 1-ethyl-3-methylimidazolium chloride ([EMIM]Cl). Their study spanned a pressure range from 35 to 150 bar, employing the T-cycle method. Their findings indicated that the inhibitory effects of these systems increase with higher concentrations and pressures. This research provides valuable insights into how these ionic liquids can influence methane phase equilibrium under various conditions. The study revealed that at lower concentrations, the inhibitory impact of the ionic liquids on methane hydrates is less pronounced. In a separate study, Menezes et al. [22] focused on evaluating the efficacy of two specific ionic liquids, [BMIM]Br and [BMIM]Cl, in inhibiting CH₄ hydrates under high-pressure conditions. This research expands the understanding of how various ionic liquids perform under different conditions, particularly in managing methane hydrate formation at elevated pressures.

Liu et al. [23] conducted the first systematic investigation into an iron-based ionic liquid as a kinetic promoter in CO₂ hydrate formation. They explored the effects of varying concentrations of [BMIM]FeCl₄ on CO₂ hydrate nucleation and growth mechanisms. According to their findings, at a concentration of 25 g/L, [BMIM]FeCl₄ significantly reduced the induction time and enhanced CO₂ storage capacity by 52.8 % and 13.7 %, respectively. Separating ionic liquids from water is crucial for their recycling. Lee et al. [24] investigated the recovery of a [BMIM]FeCl₄-rich phase from its water mixture. However, their method could not effectively distinguish between homogeneous mixtures containing up to 20 % (v/v) [BMIM]FeCl₄. Even with traditional evaporation, removing more than 80 % of water isn't straightforward due to [BMIM]FeCl₄'s hydrophobic nature, which can cause emulsion formation rather than a true solution in water. Demulsification methods have been used to separate [BMIM]FeCl₄ from water. Ultracentrifugation at 10,000 rpm did not yield significant changes, with observable [BMIM]FeCl₄ droplets settling at the vessel bottom due to their density of 1.38 g/mL [25].

This study was largely motivated by previous research conducted by Liu et al. [23], as [BMIM]FeCl₄ had not been previously explored for CO₂ hydrate formation. Besides, this is also an attempt to investigate the use of new additives for a hydrate-based solution that combines carbon capture to water treatment and/or desalination. In previous efforts, cyclopentane has been the considered additive [26,27]. In this novel study, the initial idea is to replace cyclopentane by [BMIM]FeCl₄.

Therefore, the main goals of this study are to evaluate the recovery potential of [BMIM]FeCl₄, understand its thermodynamic and kinetic effects as an additive in CO₂ hydrate formation, and examine its equilibrium behavior with water and salts under atmospheric pressure.

The work is divided into two key experimental parts: (1) the Liquid-Liquid Equilibrium (LLE) of the water + IL + salt system, and (2) the hydrate formation study. The first part focuses on how salt concentration in water influences the solubility of the ionic liquid, which is important if we aim to reuse ILs in a carbon capture process using seawater or wastewater. The second part investigates how ILs affect the thermodynamics and kinetics of CO₂ hydrate formation—whether they promote or inhibit the process.

Since the amount of IL in solution can vary depending on the salt concentration—and this in turn affects the water-to-hydrate conversion—it's essential to understand the LLE behavior first. That's why a ternary phase diagram is needed before going further.

Ultimately, this research seeks to answer a key question: Can ionic liquids like [BMIM]FeCl₄ offer a promising pathway for carbon capture?

## 2. Experimental section

### 2.1. Materials

In this study, various materials were utilized and synthesized (refer to Table 1 for molecular weights and abbreviations).

Iron (III) chloride hexahydrate was obtained from Sigma Aldrich, and 1-Butyl-3-methylimidazolium chloride (≥98.0 %) was sourced from MC2. The compound [BMIM]FeCl₄ was successfully synthesized using the method outlined by Hayashi et al. [28]. Briefly, equimolar amounts of FeCl₃·6H₂O and [BMIM]Cl were mixed under continuous stirring until [BMIM]FeCl₄ formed, resulting in a dark brown liquid. The synthesis reaction is illustrated in Fig. 1.

### 2.2. Liquid-Liquid equilibrium (LLE) set-up and protocol

#### 2.2.1. LLE set-up

An atmospheric glass batch reactor with an internal volume of 100 mL was used to measure IL solubility into salty water. Temperature control is maintained using a LAUDA RC6 CS cryostat, which operates in the range of -15 to 50 °C. Samples are weighed on a laboratory scale and added using a 2 mL volume pipette. Continuous agitation is achieved with a magnetic stirrer. Solubility temperatures are recorded manually and confirmed visually. The schematic of the experimental setup is shown in Fig. 2.

Then, A MiniSpin Plus personal microcentrifuge (Eppendorf) was utilized to perform a recovery experiment.

#### 2.2.2. LLE protocol

In a 100 ml batch reactor under atmospheric conditions, the solubility of an ionic liquid (IL) in water and brine was investigated using an isothermal method. This approach ensures precise solubility measurements by minimizing the influence of temperature variations, allowing focused evaluation of how salt affects solubility.

Initially, [BMIM]FeCl₄ was synthesized from FeCl₃·6H₂O and [BMIM]Cl. Since FeCl₃·6H₂O contains water molecules within its structure, the resulting mixture composition was 24.3 wt% water and 75.7 wt% [BMIM]FeCl₄. The reactor was filled with this mixture at atmospheric pressure and brought to the desired temperature. Subsequently, the solvent (either water or saltwater) was incrementally added in small, accurately weighed quantities until a transparent homogeneous mixture was achieved. This process was repeated for each temperature increment.

Table 2 provides an example dataset for the dissolution of IL in water. Each entry under the “Number” column denotes a step where a specific amount of water was added. The “Weighed” column indicates the pre-measured mass of water for addition, while “Left” represents the mass of water remaining after each addition. Careful consideration was

<table><caption>**Table 1**
Materials.</caption><thead><tr><th>Abbreviation</th><th>Chemical name</th><th>Supplier</th><th>Identifiers</th><th>MW</th></tr></thead><tbody><tr><td>[BMIM]Cl</td><td>1-Butyl-3-methylimidazolium chloride</td><td>MC2</td><td>CAS: 79917-90-1</td><td>174.67</td></tr><tr><td>FeCl<sub>3</sub>·6H<sub>2</sub>O</td><td>Iron(III) chloride hexahydrate</td><td>Sigma Aldrich</td><td>CAS: 10025-77-1</td><td>270.3</td></tr><tr><td>[BMIM]<br>FeCl<sub>4</sub></td><td>1-butyl-3-methylimidazolium tetrachloroferrate(III)</td><td>Synthesized</td><td></td><td>336.87</td></tr><tr><td>NaCl</td><td>Sodium chloride</td><td>Sigma Aldrich</td><td>CAS: 7647-14-5</td><td>58.44</td></tr></tbody></table>
<figure><img src="image_3.png" /><figcaption>Fig. 1. Synthesis Reaction Scheme for [BMIM]FeCl₄.</figcaption></figure>

<figure><img src="image_4.png" /><figcaption>Fig. 2. The schematic of the experimental setup for the atmospheric reactor used in the Liquid-Liquid Extraction (LLE) study.</figcaption></figure>

given to the small volume of water added, ensuring accuracy despite the minor changes in the solution mixture. Tables 3, 4 and 5 present the characteristics of reagents used and initial conditions. Uncertainties arising from this process are accounted for and documented in the Appendix B).

Water was added incrementally until the IL completely dissolved and the mixture appeared transparent. In the example shown in Table 2, complete dissolution is indicated at step "4" under the "Number" column. The final solubility result is recorded as the weight percentage of [BMIM]FeCl₄ in the solution.

Subsequent experiments involved gradually increasing the mixture's temperature by 1–2 °C, repeating the dissolution procedure at each new temperature until all required solubility data were collected.

The procedure for mixtures containing NaCl was identical, except that a brine solution was used instead of pure water. All calculations were performed following the same methodology as for the water-based experiments.

### 2.2.3. Visual observation and ultracentrifuge

To perform the visual examination test, a 100 mL solution comprising IL, NaCl, and water was prepared, with NaCl concentrations ranging from 1 wt% to 25 wt%. Samples of 10 mL each were allowed to settle undisturbed for 48 h, after which the results were visually inspected without magnification.

Additionally, selected samples containing NaCl were subjected to ultracentrifugation. Seven tubes, each containing 2.0 mL of the desired sample, were prepared to enable the separation of the IL-rich phase from the IL/brine solution (see Fig. 3). Ultracentrifugation was performed at a spin speed of 14,000 rpm for 15 min.

All samples and inorganic salts were meticulously weighed using a laboratory scale to ensure accuracy throughout the experiments.

## 2.3. Hydrate set-up for thermodynamic and kinetic studies

### 2.3.1. Apparatus description

The experimental configuration for the batch reactor closely follows previous research [27]. A diagram illustrating the experimental setup can be found in Fig. 4.

A batch reactor with a capacity of 2.23 L was constructed and utilized to investigate the phase equilibria and kinetics of clathrate hydrates. The reactor features clear windows for direct observation and is housed in an insulated shell. Internal temperature control is achieved using a LAUDA RC6 CS cryostat, capable of maintaining temperatures between –15 °C and 50 °C. The reactor was equipped with vertical agitators featuring two sets of blades: one set in the gas phase and another in the liquid phase. Temperature measurements within the reactor, including both gas and liquid phases, are monitored using two Pt100 temperature sensors positioned at the top and bottom of the cell, with an accuracy of ±0.2 °C. Pressure within the reactor is measured using a pressure probe, capable of gauging pressures from 0 to 10 MPa with a precision of ±0.1 MPa.

To introduce water, solution, and an ionic liquid into the reactor, a high-pressure Jasco pump is employed. This pump operates at flow rates ranging from 0.1 to 50 mL/min and is capable of withstanding pressures up to 10 MPa.

### 2.3.2. Hydrates experimental procedure

After thoroughly cleaning the autoclave with distilled water, a vacuum pump was employed for 15 min to remove air and impurities. The reactor was then pressurized with CO₂ to the desired pressure, with

<table><caption>**Table 3**

Characteristics of reagents.</caption><thead><tr><th>Reagents</th><th>M, g/mol</th><th>ρ, g/mL</th></tr></thead><tbody><tr><td>[BMIM]FeCl<sub>4</sub></td><td>336.87</td><td>1.38</td></tr><tr><td>H<sub>2</sub>O</td><td>18.015</td><td>1</td></tr><tr><td>[BMIM]Cl</td><td>174.68</td><td>1.086</td></tr><tr><td>FeCl<sub>3</sub>·6H<sub>2</sub>O</td><td>270.33</td><td>1.82</td></tr><tr><td>FeCl<sub>3</sub></td><td>162.2</td><td>2.9</td></tr></tbody></table>

<table><caption>**Table 2**

A set of recorded data from the solubility experiment involving an IL + water mixture at a temperature of 7.67 °C in an atmospheric reactor.</caption><thead><tr><th colspan="6">Inside the vessel</th><th colspan="3">H<sub>2</sub>O, g</th><th>T, °C</th></tr><tr><th>Number</th><th>H<sub>2</sub>O, g</th><th>IL, g</th><th>IL, ml</th><th>IL, wt%</th><th>H<sub>2</sub>O, wt%</th><th>Addition</th><th>Weighed</th><th>Left</th><th>±0.01</th></tr></thead><tbody><tr><td>0</td><td>4.4274</td><td>13.7937</td><td>9.9955</td><td>0.757</td><td>0.243</td><td>0</td><td>0</td><td>0</td><td>7.67</td></tr><tr><td>1</td><td>25.6794</td><td>13.7937</td><td>9.9955</td><td>0.3494</td><td>0.6506</td><td>21.252</td><td>21.317</td><td>0.065</td><td>7.67</td></tr><tr><td>2</td><td>25.9554</td><td>13.7937</td><td>9.9955</td><td>0.347</td><td>0.653</td><td>0.276</td><td>0.34</td><td>0.064</td><td>7.67</td></tr><tr><td>3</td><td>26.2334</td><td>13.7937</td><td>9.9955</td><td>0.3446</td><td>0.6554</td><td>0.278</td><td>0.311</td><td>0.033</td><td>7.67</td></tr><tr><td>4</td><td>26.5354</td><td>13.7937</td><td>9.9955</td><td>0.342</td><td>0.658</td><td>0.302</td><td>0.34</td><td>0.038</td><td>7.67</td></tr><tr><td>5</td><td>—//—//—</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>9.23</td></tr></tbody></table>
<table><caption>**Table 4**
Initial conditions for experiments.</caption><thead><tr><th colspan="3">1v% [BMIM]FeCl<sub>4</sub></th><th colspan="3">5v% [BMIM]FeCl<sub>4</sub></th></tr><tr><th colspan="2">Theoretical</th><th rowspan="2">n, mol</th><th colspan="2">Theoretical</th><th rowspan="2">n, mol</th></tr><tr><th>Reagents</th><th>m, g</th><th>m,g</th><th>m, g</th><th>m,g</th></tr></thead><tbody><tr><td>[BMIM]FeCl<sub>4</sub></td><td>1.38</td><td rowspan="3">0.0041</td><td>6.9</td><td rowspan="3">0.021</td><td>3.57</td></tr><tr><td>[BMIM]Cl</td><td>0.72</td><td>3.58</td><td>5.54</td></tr><tr><td>FeCl<sub>3</sub>·6H<sub>2</sub>O</td><td>1.11</td><td>5.54</td><td>5.54</td></tr><tr><td>Solution</td><td>100</td><td>100</td><td>100</td><td>100</td><td>100</td></tr></tbody></table>

<table><caption>**Table 5**
Initial reagent conditions for visual and ultracentrifuge experiments.</caption><thead><tr><th colspan="6">1v% [BMIM]FeCl<sub>4</sub></th></tr><tr><th colspan="3">Theoretical</th><th colspan="3">Experimental</th></tr><tr><th>Number</th><th>NaCl, wt\%</th><th>NaCl, g</th><th>Solution, g</th><th>NaCl, g</th><th>Solution, g</th><th>V(sample), ml</th></tr></thead><tbody><tr><td>1</td><td>1</td><td>0.1</td><td>10</td><td>0.1</td><td>10</td><td>2</td></tr><tr><td>2</td><td>3.5</td><td>0.35</td><td>10</td><td>0.35</td><td>10.02</td><td>2</td></tr><tr><td>3</td><td>5</td><td>0.5</td><td>10</td><td>0.5</td><td>10.01</td><td>2</td></tr><tr><td>4</td><td>10</td><td>1</td><td>10</td><td>1.04</td><td>10.01</td><td>2</td></tr><tr><td>5</td><td>15</td><td>1.5</td><td>10</td><td>1.51</td><td>10.01</td><td>2</td></tr><tr><td>6</td><td>20</td><td>2</td><td>10</td><td>2</td><td>10.01</td><td>2</td></tr><tr><td>7</td><td>25</td><td>2.5</td><td>10</td><td>2.5</td><td>10.04</td><td>2</td></tr></tbody><thead><tr><th colspan="6">5v% [BMIM]FeCl<sub>4</sub></th></tr><tr><th colspan="3">Theoretical</th><th colspan="3">Experimental</th></tr><tr><th>Number</th><th>NaCl, wt\%</th><th>NaCl, g</th><th>Solution, g</th><th>NaCl, g</th><th>Solution, g</th><th>V(sample), ml</th></tr></thead><tbody><tr><td>1</td><td>1</td><td>0.1</td><td>10</td><td>0.1</td><td>10.05</td><td>2</td></tr><tr><td>2</td><td>3.5</td><td>0.35</td><td>10</td><td>0.35</td><td>10.06</td><td>2</td></tr><tr><td>3</td><td>5</td><td>0.5</td><td>10</td><td>0.5</td><td>10</td><td>2</td></tr><tr><td>4</td><td>10</td><td>1</td><td>10</td><td>1</td><td>10</td><td>2</td></tr><tr><td>5</td><td>15</td><td>1.5</td><td>10</td><td>1.5</td><td>10.08</td><td>2</td></tr><tr><td>6</td><td>20</td><td>2</td><td>10</td><td>2</td><td>10.01</td><td>2</td></tr><tr><td>7</td><td>25</td><td>2.5</td><td>10</td><td>2.51</td><td>10.02</td><td>2</td></tr></tbody></table>

Absolute uncertainty for measurements is 0.01 g.

temperature and pressure maintained constant for 24 h to confirm the absence of gas leaks.

An ionic liquid or ionic liquid + salt solution at the specified concentration was prepared immediately before injection into the reactors. Using an HPLC pump, 400 mL of the solution were introduced into the reactor. Subsequently, the temperature was lowered to 1 °C.

The pressure-time and temperature-time curves for each experiment are detailed and analyzed below (refer to Fig. 5). Each experiment began at point A, representing the initial state outside the hydrate formation region, immediately after material injection, with the system subsequently cooled to approximately 1 °C. After allowing several hours for gas dissolution into the liquid phase and the induction period, crystallization initiated at point B. Hydrate formation was accompanied by a slight, temporary rise in temperature.

To achieve equilibrium, the system was maintained under these conditions for 2–3 days, during which no further changes in temperature or pressure were observed. Hydrate formation was considered complete at point C. The duration required to reach equilibrium varied depending on the initial concentration of the aqueous solution and the applied pressure.

Subsequently, hydrate dissociation was induced by gradually increasing the system temperature until the dissociation curve reached its final equilibrium point D. Note that point D also correspond to the intersection between the initial cooling curve and the heating curve.

### 2.3.3. *Experimental conditions*

The experimental conditions for all experiments conducted in this part are summarized below, alongside the corresponding experiment names:

## 3. Calculation methods for hydrates kinetic study

### 3.1. Determination of moles in the hydrate phase

The initial quantity of gases in the reactor is distributed among the gaseous, liquid, and solid hydrate phases within the system. Therefore, at equilibrium, the amount of gas incorporated into the hydrate phase can be determined using a mass balance approach:

<figure><img src="image_5.png" /><figcaption>**Fig. 3.** Samples of IL + NaCl solutions subjected to ultracentrifugation experiment.</figcaption></figure>
<figure><img src="image_6.png" /><figcaption>Fig. 4. The diagram depicting the experimental setup for hydrate studies.</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>Fig. 5. Pressure-time and temperature-time curves depicting CO2 hydrate crystallization and dissociation.</figcaption></figure>

$$n^T = n^L + n^G + n^H \qquad (1)$$

In Eq. (1), $n^T$ denotes the initial total number of moles in the system. The variables $n^H$, $n^L$ and $n^G$ represent the mole numbers of the gas component in the hydrate, liquid, and gas phases, respectively.

The total number of moles of gas in the gas phase at any equilibrium state, $n^G$, can be calculated using the well-known Eq. (2).

$$n^G = \frac{PV^R}{Z(T, p, y_{j,0})RT} \qquad (2)$$

In this context, $T$, $P$, and $V^R$ represent the temperature, pressure, and total volume of the system, respectively. The parameter $y_{j,0}$ is set to 1, as only a single component is involved. $R$ denotes the universal gas
constant. The compressibility factor, Z, can be determined using an equation of state (EOS), such as a classic cubic EOS. For this study, the Soave-Redlich-Kwong (SRK) EOS was employed, with parameters taken from Danesh [29]. The total volume of the reactor, V<sup>R</sup>, is 2.23 L (SECOHYA).

At equilibrium, the gases exhibit equal fugacity in both the liquid and gas phases, in accordance with the following principle:

$$f_j^L(T, P, x_j) = f_j^G(T, P, y_j) \qquad (3)$$

By substituting the liquid phase fugacity with an expanded version of Henry's law and expressing the gas phase fugacity in terms of the fugacity coefficient in equation (4), we obtain an equation for the molar amount n<sup>L</sup> of gas dissolved in the liquid phase.

$$n_j^L = \frac{V^L \rho_w^\circ}{M_w} \frac{y_j \varphi_j^G P}{K_{H,j}^\infty \exp(P v_j^\infty / RT)} \qquad (4)$$

In Eq. (4), V<sup>L</sup> denotes the volume of the liquid phase at equilibrium, ρ<sup>o</sup><sub>w</sub> represents the density, and M<sub>w</sub> is the molar mass of pure water. v<sup>∞</sup><sub>j</sub> = 32 cm<sup>3</sup> mol<sup>-1</sup> refers to the partial molar volume of gas j in the solvent water, an average value from Holder [30]. When deriving Eq. (5), the activity coefficient of CO<sub>2</sub> in water was effectively disregarded, and the approximation n<sup>L</sup><sub>j</sub> ≪n<sup>L</sup><sub>w</sub> was applied. K<sup>∞</sup><sub>H,j</sub> (Pa<sup>-1</sup>) represents Henry's constant at the saturation pressure of the pure solvent, i.e., at infinite dilution of the gaseous component. This constant, which varies with temperature, is computed using the following correlation provided by Holder [30].

$$K_{H,j}^{\infty} = \exp\left(-A - \frac{B}{T}\right) \qquad (5)$$

Constants A and B comes from previous study (A is equal to 14.28315 and B to -2050.327) [30].

Note that, in this first approach, the influence of IL on carbon dioxide on aqueous phase solubility is neglected since not data could be found in the literature. This simplifies the calculation and assumes that the additives, which are present at relatively low concentrations (5 vol% for [BMIM]FeCl<sub>4</sub> and 3.5 wt% for NaCl), do not significantly alter the solubility of CO<sub>2</sub> in the water phase. Additionally, Henry's law constant takes infinite dilution as reference, assuming the pure solvent condition. Given the small concentration of the additives in the liquid phase, one could assume that this is a good first approach. Still, better consideration of the additives could enhance the model.

However, we agree that a more detailed model accounting for the activity coefficients of CO<sub>2</sub> in the presence of these additives could be beneficial for future studies, and we will consider this in subsequent work.

Then, during the formation of the hydrate, the volume of the reactor is given by:

$$V^R = V^L + V^G + V^H \qquad (6)$$

Here, V<sup>R</sup> represents the volume of the reactor, while V<sup>L</sup>, V<sup>G</sup>, and V<sup>H</sup> denote the volumes of the liquid, gas, and hydrate phases, respectively. The volumes of the liquid and hydrate phases can be calculated using Eqs. (7) and (8).

$$V^L = \frac{n_W^L \cdot M_W}{\rho_W} \qquad (7)$$

$$V^H = \frac{n_W^H \cdot M_W}{\rho_H} \qquad (8)$$

where n<sup>L</sup><sub>w</sub> represents the total number of moles of water, while n<sup>L</sup><sub>w</sub> and n<sup>H</sup><sub>w</sub> denote the mole numbers of water in the liquid and hydrate phases, respectively. Additionally, ρ<sub>w</sub> and ρ<sub>H</sub> indicate the densities of water and hydrate, respectively.

By neglecting n<sup>G</sup><sub>w</sub>, it can be assumed that:

$$n_w^T = n_w^L + n_w^H \qquad (9)$$

and

$$n^H = \frac{n_w^H}{N_{\text{hyd}}} \qquad (10)$$

where N<sub>hyd</sub> represents the maximum hydration number, which is 5.75 for sl hydrate. By estimating the mole number of water in the hydrate phase, denoted as n<sup>H</sup><sub>w</sub>, and utilizing the previously provided equations, we calculated the amount of hydrate formed during the crystallization process. A diagrammatic representation of the model is shown in Fig. 6.

By setting an initial value for the mole number of water in the hydrate phase, n<sup>H</sup><sub>w</sub>, we verify the equivalence of n<sup>H</sup> obtained from Eq. (1) and n<sup>H</sup> from Eq. (10). In our model, this resulting n<sup>H</sup> value is referred to as n<sup>H</sup><sub>est</sub>. If the comparison confirms a match, we finalize the calculation and retrieve the results. However, if there is a discrepancy, we adjust the mole number of water in the hydrate phase, referred to as n<sup>H</sup><sub>w</sub>.

## 3.2. Calculations for $k_l^{GL}$a and $k_l^{LH}$a

### 3.2.1. From the gas phase to the liquid phase

The solubility of carbon dioxide during the hydration process is evaluated based on the mass transfer coefficient. This coefficient is influenced by various factors, such as the properties of the gas and liquid involved, the environmental conditions of the system, and its physical configuration. To break down the process of assessing the transfer rate (or consumption rate, r<sub>j</sub>):

$$r_j = - \frac{dn_j^G}{dt} = \frac{dn_j^L}{dt} \qquad (11)$$

The variation in dn<sup>G</sup><sub>j</sub> correlates directly with changes in pressure, assuming of constant gas volume and stable temperature.

$$dn_j^G = \frac{V^G}{ZRT} dP \qquad (12)$$

The following equation illustrates the transfer of a gas into the liquid at their interface:

$$r_j^{GL} = k_l^{GL} a \times V^L \frac{\rho_W}{M_W} \left( x_j^{GL,\text{int}} - x_j^{L,\text{bulk}} \right) \qquad (13)$$

Therefore, the left-hand side of Eq. (11) can be readily determined using dP (derived from experimental data) and Z (obtained from an equation of state, such as SRK).

In Eq. (13), r<sup>GL</sup><sub>j</sub> denotes the rate at which CO<sub>2</sub> dissolves into the liquid. The term x<sup>GL, int</sup><sub>j</sub> represents the molar fraction of gas j at the gas-liquid interfaces, while x<sup>L, bulk</sup><sub>j</sub> denotes the molar fraction of gas j in the bulk of the liquid. V<sup>L</sup><sub>W</sub>, ρ<sub>W</sub>, and M<sub>W</sub> correspond to the volume, density, and molar mass of liquid water, respectively. Finally, k<sup>GL</sup><sub>l</sub> and k<sup>LH</sup><sub>l</sub> represent the mass transfer coefficients for the gas-to-liquid and liquid-to-hydrate phases, respectively, scaled by the interfacial surface area, since their specific values are not individually specified.

The molar fraction of gas j at the interface, denoted as x<sup>int</sup><sub>j</sub>, is considered to be in thermodynamic equilibrium. This equilibrium condition is practically applied using Henry's law, resulting in:

$$x_j^{GL,\text{int}} = \frac{x_j^G \varphi_j^G P}{K_{H,j}^{\infty} \exp\left((P - P^{\text{sat}}) v_j^{\infty} / RT\right)} \qquad (14)$$

where K<sup>∞</sup><sub>H,j</sub> has been previously discussed in Eqs. (4) and (5).

The concentration of gas j in the bulk of the liquid, denoted as x<sup>L, bulk</sup><sub>j</sub>,
<figure><img src="image_8.png" /><figcaption>Fig. 6. A schematic representation of the model employed to compute the mole number of the hydrate.</figcaption></figure>

is influenced by the amount of gas dissolved in the liquid water. To streamline our calculations, we make the following assumption: in the liquid phase, the number of moles of water is significantly greater than the number of moles of dissolved gas, meaning $n_j^L \ll n_W^L$. Thus,

$$x_j^{L,bulk} = \frac{n_j^L}{n_W^L} \qquad (15)$$

$$d x_j^{L, bulk} \times n_W^L = \frac{V^G}{ZRT} dP \qquad (16)$$

By integrating the previously mentioned equation over the interval from $t = 0$ to $t$, we obtain the following result:

$$x_j^{L,bulk}(t) - x_j^{L,bulk}(t=0) = \frac{V^G}{ZRTn_W^L} (P(t) - P(t=0)) \qquad (17)$$

either

$$x_j^{L,bulk}(t) = \frac{V^G}{ZRTn_W^L} (P(t) - P^0) \qquad (18)$$

By applying the relationships outlined in equations (11), 13, and 14, and 18, we derive the following expression:

$$k_l^{GL} a = \frac{\frac{V^G}{ZRT} \frac{dP}{dt}}{\left( \frac{n_W^L P}{K_{H,j}^{LH} \exp\left(\frac{P-P_{sat}}{V^G/RT}\right)} - \frac{V_G}{ZRT} (P-P^0) \right)} \qquad (19)$$

Fig. 7 presents a schematic representation of the progressive material transfer process within the aqueous phase and the hydrate crust.

### 3.2.2. From the liquid phase to the hydrate phase

The equation below illustrates the transfer of a liquid into a solid at their interface:

$$r_j^{LH} = k_l^{LH} a \times V_w^L \frac{\rho_W}{M_W} \left( x_j^{LH, int} - x_j^{L,bulk} \right) \qquad (20)$$

here $r_j^{LH}$ represents the rate at which CO₂ dissolves into the solid (hydrate phase). The term $x_j^{LH, int}$ denotes the molar fraction of gas j at the interfaces between liquid and solid. Detailed discussion of parameters such as $x_j^{LH, int}$ and $x_j^{L,bulk}$ will be provided in the Results and Discussion sections. This approach is crucial due to specific assumptions made to address limitations and ensure consistency with existing data.

## 4. Results and discussion

### 4.1. Il-solution Liquid-Liquid equilibrium (LLE)

A study of the equilibrium between [BMIM]FeCl₄ and water began with a visual inspection and an ultracentrifuge experiment to evaluate the effectiveness of separating the ionic liquid from water using the decantation method. Fig. 4 illustrates the samples prepared for the ultracentrifugation process. Prior to conducting any experiments, it was observed that the presence of salt, and its increasing concentration, deepened the yellow coloration of the mixture.

Table 6 presents the evaluation of seven combinations of IL-water mixtures with salt concentrations ranging from 1 to 25 wt%. Observation 1 involved a visual inspection with the naked eye using a 10 mL tube, while Observation 2 analyzed the outcomes following ultracentrifugation. Each observation was categorized as “poor,” “mid,” or “good.” In this context, “poor” indicated a homogeneous mixture, “mid” indicated the presence of visible IL bubbles, and “good” indicated the formation of a substantial IL layer.

According to the table, no visible changes were observed in either experiment when 1 wt% IL was mixed with NaCl brine concentrations
<figure><img src="image_9.png" /><figcaption>**Fig. 7.** Diagrammatic depiction of the diffusion and reaction layers involved in the process of hydrate crystallization.</figcaption></figure>

ranging from 1 to 25 wt%. A similar trend persisted with 5 wt% IL mixtures in NaCl brines ranging from 1 to 15 wt%. However, with a 20 wt% NaCl mixture, IL bubbles became noticeable during the initial experiment, and after ultracentrifugation, a significant IL layer accumulated at the bottom of the tube. Moreover, the mixture of 5 wt% IL with 25 wt% NaCl exhibited the most favorable results in both

observational assessments, earning a “good” rating.

Nevertheless, it is important to note that these findings only indicated the presence of a distinct IL layer, while the upper phase remained homogeneous with a yellowish tint. Based on these observations, it was concluded that the solubility of [BMIM]FeCl₄ decreases in the presence of NaCl.
<table><caption>**Table 6**
Experimental outcomes from visual inspection and ultra-centrifugation analyses.</caption><thead><tr><th colspan="5">1v% [BMIM]FeCl<sub>4</sub></th><th colspan="5">Experimental</th></tr><tr><th colspan="4">Theoretical</th><th colspan="4">Experimental</th></tr><tr><th>Number</th><th>NaCl, wt\%</th><th>NaCl, g</th><th>Solution, g</th><th>NaCl, g</th><th>Solution, g</th><th>V(sample), ml</th><th>Observation 1</th><th>Observation 2</th></tr></thead><tbody><tr><td>1</td><td>1</td><td>0.1</td><td>10</td><td>0.0995</td><td>10.0025</td><td>2</td><td>poor</td><td>poor</td></tr><tr><td>2</td><td>3.5</td><td>0.35</td><td>10</td><td>0.3541</td><td>10.0174</td><td>2</td><td>poor</td><td>poor</td></tr><tr><td>3</td><td>5</td><td>0.5</td><td>10</td><td>0.501</td><td>10.0107</td><td>2</td><td>poor</td><td>poor</td></tr><tr><td>4</td><td>10</td><td>1</td><td>10</td><td>1.0438</td><td>10.0131</td><td>2</td><td>poor</td><td>poor</td></tr><tr><td>5</td><td>15</td><td>1.5</td><td>10</td><td>1.5051</td><td>10.0069</td><td>2</td><td>poor</td><td>poor</td></tr><tr><td>6</td><td>20</td><td>2</td><td>10</td><td>2.0016</td><td>10.0067</td><td>2</td><td>poor</td><td>poor</td></tr><tr><td>7</td><td>25</td><td>2.5</td><td>10</td><td>2.5013</td><td>10.0401</td><td>2</td><td>poor</td><td>poor</td></tr></tbody></table><table><thead><tr><th colspan="5">5v% [BMIM]FeCl<sub>4</sub></th><th colspan="5">Experimental</th></tr><tr><th colspan="4">Theoretical</th><th colspan="4">Experimental</th></tr><tr><th>Number</th><th>NaCl, wt\%</th><th>NaCl, g</th><th>Solution, g</th><th>NaCl, g</th><th>Solution, g</th><th>V(sample), ml</th><th>Observation 1</th><th>Observation 2</th></tr></thead><tbody><tr><td>1</td><td>1</td><td>0.1</td><td>10</td><td>0.1011</td><td>10.0549</td><td>2</td><td>poor</td><td>poor</td></tr><tr><td>2</td><td>3.5</td><td>0.35</td><td>10</td><td>0.3538</td><td>10.0561</td><td>2</td><td>poor</td><td>poor</td></tr><tr><td>3</td><td>5</td><td>0.5</td><td>10</td><td>0.5035</td><td>10.0001</td><td>2</td><td>poor</td><td>poor</td></tr><tr><td>4</td><td>10</td><td>1</td><td>10</td><td>1.0042</td><td>10.0021</td><td>2</td><td>poor</td><td>poor</td></tr><tr><td>5</td><td>15</td><td>1.5</td><td>10</td><td>1.5021</td><td>10.0779</td><td>2</td><td>poor</td><td>poor</td></tr><tr><td>6</td><td>20</td><td>2</td><td>10</td><td>2.0009</td><td>10.0081</td><td>2</td><td>mid</td><td>good</td></tr><tr><td>7</td><td>25</td><td>2.5</td><td>10</td><td>2.5062</td><td>10.0214</td><td>2</td><td>good</td><td>good</td></tr></tbody></table>

"poor" signifies that the mixture remains homogeneous.

"mid" denotes that the bubbles of IL are visible.

"good" signifies that the mixture remains homogeneous.

Consequently, our subsequent investigation focused on examining the solubility of [BMIM]FeCl₄. The outcomes obtained from the atmospheric reactor for the ionic liquid (IL) in water and water/salt mixtures are detailed in Table 7.

Fig. 8 illustrates the saturation curve, where the error bars are smaller than the symbols representing the data points. This curve shows a decreasing trend. The area above the curve indicates supersaturation, while the area below indicates undersaturation.

All graphs consistently demonstrate a decrease in [BMIM]FeCl₄ solubility with increasing temperature. Specifically, for the IL-water mixture, the solubility of [BMIM]FeCl₄ decreased from 51.98 g per 100 g of water to 45.82 g per 100 g of water over the temperature range of 7.67–20 °C.

Compared to the linear model proposed by Toler et al. [31] (R² = 0.9899), our findings demonstrate satisfactory agreement.

$$y = -0.072x + 0.7379 \quad (21)$$

In this context, y represents the logarithm of $log(C_{iw}^{sat})$, where $C_{iw}^{sat}$ denotes the solubility of an organic liquid in water, measured in mL/L [32]. The molar volume is represented by x, the molar volume in mL/mol. According to the model, the expected solubility of [BMIM]FeCl₄ is approximately 54.28 g per 100 g of water.

The presence of NaCl in the system notably reduced the solubility of [BMIM]FeCl₄. For instance, at 7.6 °C with 2 wt% NaCl, the solubility of [BMIM]FeCl₄ decreased by 13 %. This effect is particularly evident in the final blue curve, corresponding to NaCl concentrations of 12–14 wt %. The sharp decline in solubility can be attributed to both the reduced solubility of [BMIM]FeCl₄ at higher temperatures and the increased NaCl concentration.

Several hypotheses attempt to explain this phenomenon. One consideration involves thermodynamic factors, specifically temperature effects. In systems containing both NaCl and IL, the solubility of NaCl typically increases with rising temperature, whereas that of the IL decreases. It is speculated that chloride ions from NaCl may interact with the IL structure, potentially forming complexes around Fe, thereby reducing its solubility. Another plausible explanation is the “salting-out” effect induced by NaCl, a well-known phenomenon in separation processes where salts are used to extract ionic liquids from aqueous

<table><caption>**Table 7**
Experimental findings acquired from the atmospheric reactor.</caption><thead><tr><th colspan="7">[BMIM]FeCl<sub>4</sub> + H<sub>2</sub>O</th></tr><tr><th>T, °C</th><th>[BMIM]<br>FeCl<sub>4</sub>, wt\%</th><th>H<sub>2</sub>O, wt<br>\%</th><th>NaCl,<br>wt%</th><th>Solubility, g/<br>100 g H<sub>2</sub>O</th><th>Solubility, g<br>unc.</th></tr></thead><tbody><tr><td>7.67</td><td>34.23</td><td>65.77</td><td>0</td><td>52</td><td>±0.08</td></tr><tr><td>9.23</td><td>33.77</td><td>66.23</td><td>0</td><td>50.95</td><td>±0.09</td></tr><tr><td>10.82</td><td>33.27</td><td>66.73</td><td>0</td><td>49.82</td><td>±0.09</td></tr><tr><td>12.37</td><td>32.82</td><td>67.18</td><td>0</td><td>48.81</td><td>±0.1</td></tr><tr><td>16.35</td><td>32.11</td><td>67.89</td><td>0</td><td>47.26</td><td>±0.1</td></tr><tr><td>20</td><td>31.45</td><td>68.55</td><td>0</td><td>45.84</td><td>±0.1</td></tr></tbody><thead><tr><th colspan="7">[BMIM]FeCl<sub>4</sub> + H<sub>2</sub>O + 2 wt% NaCl</th></tr><tr><th>T, °C</th><th>[BMIM]<br>FeCl<sub>4</sub>, wt\%</th><th>H<sub>2</sub>O, wt<br>\%</th><th>NaCl,<br>wt%</th><th>Solubility, g/<br>100 g H<sub>2</sub>O</th><th>Solubility, g<br>unc.</th></tr></thead><tbody><tr><td>7.6</td><td>30.69</td><td>67.23</td><td>2.08</td><td>45.65</td><td>±0.08</td></tr><tr><td>9.49</td><td>30.04</td><td>67.85</td><td>2.11</td><td>44.28</td><td>±0.08</td></tr><tr><td>11.24</td><td>29.5</td><td>68.36</td><td>2.14</td><td>43.16</td><td>±0.09</td></tr><tr><td>13.14</td><td>28.9</td><td>68.94</td><td>2.16</td><td>41.91</td><td>±0.09</td></tr><tr><td>14.9</td><td>28.79</td><td>69.05</td><td>2.17</td><td>41.69</td><td>±0.09</td></tr><tr><td>18.58</td><td>28.17</td><td>69.63</td><td>2.2</td><td>40.46</td><td>±0.09</td></tr><tr><td>20.38</td><td>27.54</td><td>70.23</td><td>2.23</td><td>39.22</td><td>±0.09</td></tr></tbody><thead><tr><th colspan="7">[BMIM]FeCl<sub>4</sub> + H<sub>2</sub>O + 12–14 wt% NaCl</th></tr><tr><th>T, °C</th><th>[BMIM]<br>FeCl<sub>4</sub>, wt\%</th><th>H<sub>2</sub>O, wt<br>\%</th><th>NaCl,<br>wt%</th><th>Solubility, g/<br>100 g H<sub>2</sub>O</th><th>Solubility, g<br>unc.</th></tr></thead><tbody><tr><td>7.5</td><td>24.74</td><td>63.25</td><td>12.02</td><td>39.11</td><td>±0.08</td></tr><tr><td>9.3</td><td>23.93</td><td>63.87</td><td>12.21</td><td>37.46</td><td>±0.08</td></tr><tr><td>11.14</td><td>22.02</td><td>65.32</td><td>12.66</td><td>33.71</td><td>±0.08</td></tr><tr><td>12.7</td><td>20.7</td><td>66.33</td><td>12.97</td><td>31.15</td><td>±0.08</td></tr><tr><td>14.7</td><td>19.79</td><td>67.03</td><td>13.18</td><td>29.24</td><td>±0.07</td></tr><tr><td>17.5</td><td>17.81</td><td>68.54</td><td>13.65</td><td>25.25</td><td>±0.06</td></tr><tr><td>19.65</td><td>15.89</td><td>70.01</td><td>14.1</td><td>21.72</td><td>±0.05</td></tr></tbody></table>

Absolute uncertainty for Temperature is 0.01 °C.

solutions.

Finally, Fig. 9 shows the observed LLE in the form of a ternary diagram.
<figure><img src="image_10.png" /><figcaption>Fig. 8. The solubility curve of [BMIM]FeCl4 in various systems.</figcaption></figure>

## 4.2. Study of the thermodynamics and kinetics of hydrate formation

### 4.2.1. Carbon dioxide hydrate formation — Thermodynamic study

Subsequently, our focus shifted to investigating the influence of the ionic liquid (IL) on hydrate formation. To examine the thermodynamic impact of IL on CO₂ hydrate crystallization, we initiated experiments with 5 vol% IL and observed its subsequent dissociation.

Fig. 10 shows that the addition of 5 vol% IL did not significantly alter the system's thermodynamics. The equilibrium point (labeled as D) at 278.3 K and 23.4 bar aligns closely with the equilibrium curve of pure CO₂ hydrate, as reported by Adisasmito et al. [33].

Next, we conducted experiments involving CO₂ hydrate formation

with 5 vol% IL and 3.5 wt% NaCl. The pressure-temperature (P-T) trajectory (Fig. 11) was compared with multiple literature datasets [34–36]. We found that the combined presence of NaCl and [BMIM] FeCl₄ exhibited a more pronounced inhibitory effect on hydrate formation compared to 3.5 wt% NaCl alone.

The experimental equilibrium point for CO₂ hydrate dissociation in the presence of 5 vol% IL and 3.5 wt% NaCl was determined to be 278.5 K and 24.4 bar. This equilibrium point closely resembled that observed for a system containing 7 wt% NaCl, as reported by Nakane et al. [34].

According to Nakane et al. [34], the presence of 3.5 wt% NaCl reduces the equilibrium temperature by $\Delta T = 1.5$ K compared to pure CO₂ hydrate. In our study, the addition of both 5 vol% [BMIM]FeCl₄ and 3.5

<figure><img src="image_11.png" /><figcaption>Fig. 9. Ternary phase diagram for the water-IL-NaCl system within the temperature range of 280.74–290.63 K.</figcaption></figure>

<figure><img src="image_12.png" /><figcaption>Fig. 10. Pressure and Temperature curve of CO₂ hydrate in the presence of 5 vol% [BMIM]FeCl₄ in comparison with the literature data [33].</figcaption></figure>
<figure><img src="image_13.png" /><figcaption>**Fig. 11.** Pressure and Temperature curve of CO₂ hydrate in the presence of 5v% of [BMIM]FeCl₄ and 3.5 wt% NaCl in compared with the literature data [33–36].</figcaption></figure>

wt% NaCl resulted in a greater temperature reduction of ΔT = 2.9 K compared to the pure CO₂ hydrate equilibrium curve from Adisasmito et al. [33].

### 4.2.2. Carbon dioxide hydrate formation — Kinetic study

A crucial aspect in determining the amount of hydrate formed during crystallization is the hydration number. The question arises whether this number is dynamic throughout the crystallization process or can be reasonably assumed to remain constant.

Our experimental findings enabled us to establish a range for the hydration number. We tested two distinct hydration numbers, $N_{hyd}$ = 5.5 and 6.4, based on common values reported in the literature. These numbers correspond to the ideal stoichiometries of structure I (sI) hydrates.

Referring to Fig. 11, it is evident that for the first 220 min after induction, the differences across the hydration numbers are negligible. However, a noticeable divergence occurs as crystallization nears completion. The final hydrate quantities are 1.466 and 1.484 mol for hydration numbers 5.5 and 6.4, respectively, indicating an approximate uncertainty of 1.3 % per hydration number. It is important to note that this uncertainty pertains strictly to total crystallization, and the uncertainty during the crystallization phase would be lower. Based on literature sources [37,38], we have designated the hydration number as 5.75, considering it the maximum for the sI structure in all our $n^H$ computations.

Fig. 12 illustrates the amounts of CO₂ in the hydrate phase for three different systems: pure CO₂, CO₂ with [BMIM]FeCl₄, and CO₂ with both [BMIM]FeCl₄ and 3.5 wt% NaCl. It is important to note that the time axis is normalized to the induction time for each system, marking the point at which nucleation begins. Consequently, direct comparisons based solely on the x-axis may not provide precise insights.

In the CO₂ + [BMIM]FeCl₄ + NaCl system, the cooling protocol that was effective for pure CO₂ and CO₂ + [BMIM]FeCl₄ did not initially result in hydrate formation. As a result, the temperature was further lowered to promote additional hydrate growth for comparative analysis. Initially, only 0.08 mol of CO₂ were captured in the hydrate phase using

<figure><img src="image_14.png" /><figcaption>**Fig. 12.** Investigating the variation of $n^H$ with two distinct hydration numbers during pure CO₂ hydrate crystallization.</figcaption></figure>

the original cooling method for the CO₂ + [BMIM]FeCl₄ + NaCl system, corresponding to the early post-induction point observed in the CO₂ + [BMIM]FeCl₄ system. A subsequent, more aggressive cooling protocol enabled the capture of 0.4 mol of CO₂. In Fig. 13, for the CO₂ + [BMIM]FeCl₄ + NaCl system, we present the second phase of CO₂ accumulation in the hydrate, which explains why the corresponding curve appears shorter compared to those for pure CO₂ and CO₂ + [BMIM]FeCl₄.

Based on the experimental data we collected, we determined the mass transfer constants during dissolution $k_l^{GL}a$ and crystallization $k_l^{H}a$ for pure CO₂, CO₂ + [BMIM]FeCl₄, and CO₂ + [BMIM]FeCl₄ + NaCl.

First, we divided crystallization kinetics into two parts:
<figure><img src="image_15.png" /><figcaption>Fig. 13. Amount of CO₂ in the hydrate phrase across various systems.</figcaption></figure>

1. **Gas to Liquid:** covering the dissolution and diffusion of gas up to the initial nucleation event (induction time).

2. **Liquid to Solid:** involving nucleation and hydrate growth up to total crystallization (post-induction).

Several assumptions were made during our calculations, and these are annotated alongside the respective results for clarity.

Referring to Equations (13) and (20) discussed earlier, the outcomes are summarized below:

Remark:

* Gas dissolution during the initial injection into the tank filled with the liquid phase was not considered. The evaluation of the gas-liquid mass transfer coefficient ($k_l^{GL}a$) focuses solely on the dissolution and diffusion after the system was initially pressurized.

* Thermodynamic equilibrium at the gas-water interface was assumed, and mass transfer was assessed from the gas-liquid boundary to the bulk liquid.

Fig. 14 presents the mass transfer constants for the gas-to-liquid phase in the three systems. The $k_l^{GL}a$ for the pure CO₂ hydrate system was determined to be 1.58·10⁻⁴ s⁻¹. In comparison, the mass transfer coefficients for the CO₂ + [BMIM]FeCl₄ and CO₂ + [BMIM]FeCl₄ + NaCl systems were 5.2·10⁻⁷ s⁻¹ and 2.15·10⁻⁷ s⁻¹, respectively.

Thus, the addition of 5 vol% [BMIM]FeCl₄, either alone or in combination with 3.5 wt% NaCl, significantly reduced the dissolution rate of CO₂ — by approximately three orders of magnitude.

To determine the mass transfer coefficient from the liquid bulk to the hydrate interface during the liquid-to-solid transition, we made the following assumptions:

* Thermodynamic equilibrium in liquid phase: Equilibrium is established between the gas-liquid interface and the bulk liquid phase at the operating temperature and the corresponding equilibrium pressure during nucleation and hydrate growth. This implies $x_j^{GL,int} = x_j^{L,bulk}$.

* Thermodynamic equilibrium at hydrate interface: The hydrate interface concentration $x_j^{L,int}$ is assumed to be in thermodynamic equilibrium, achieved at the end of the experiment during complete crystallization under final pressure ($P_f$) and temperature ($T_f$) conditions.

* CO₂ consumption measurement: The consumption of CO₂ was measured in moles per second, with data recorded at 10-minute intervals.

<figure><img src="image_16.png" /><figcaption>Fig. 14. Mass transfer coefficients from gas to liquid for three different systems.</figcaption></figure>

Fig. 15 illustrates the evolution of $k_l^{LHA}$ a during the liquid-to-solid transfer process for pure CO₂ hydrate formation. Initially, our assumptions hold well immediately after the induction time. However, as time progresses, noticeable fluctuations in the calculated values are observed. Upon closer examination of the region highlighted in red, a relatively consistent range between 2.36·10⁻⁴ and 4·10⁻⁴ is evident over the 240 min following the initial nucleation event.

The average $k_l^{LHA}$ for the liquid-solid transfer in the pure CO₂ system was calculated to be 3.1·10⁻⁴ s⁻¹. For the system containing [BMIM]FeCl₄, $k_l^{LHA}$ was determined to be 8.7·10⁻⁴ s⁻¹, while for the system combining [BMIM]FeCl₄ with NaCl, the value was 5.3·10⁻⁴ s⁻¹. Additional graphical representations of the $k_l^{LHA}$ a evolution for the CO₂ + [BMIM]FeCl₄ and CO₂ + [BMIM]FeCl₄ + NaCl systems are provided in Appendix A (Figs. A.1 and A.2).

Our experimental results confirm that the gas-liquid transfer is the rate-limiting step in the overall hydrate formation process.

## 5. Conclusion

In summary, the introduction of [BMIM]FeCl₄ as an ionic liquid (IL) in this study clearly demonstrated its inhibitory effect on CO₂ hydrate

<figure><img src="image_17.png" /><figcaption>Fig. 15. Variation of the liquid to hydrate mass transfer coefficient ($k_l^{LHA}$) for pure CO₂.</figcaption></figure>
formation. Moreover, when combined with NaCl, the system exhibited an even more pronounced inhibitory impact.

In the atmospheric reactor liquid-liquid equilibrium (LLE) study, it was observed that the solubility of [BMIM]FeCl₄ in water increases as the temperature decreases, whereas the solubility of NaCl shows the opposite trend. Based on these findings, a phase diagram for the ternary system of water, [BMIM]FeCl₄, and NaCl was constructed.

Considering the outcomes from visual observations, ultra-centrifuge experiments, and the LLE study conducted in the atmospheric reactor, we concluded that the chemical method effectively separates the bulk layer of [BMIM]FeCl₄ from a homogeneous solution, particularly at concentrations of 5 vol% and above. For thorough purification, an additional evaporation step is recommended to remove any residual H₂O from the extracted [BMIM]FeCl₄. The significant solubility of these ILs in water highlights their unsuitability for water-based extraction processes, emphasizing the importance of assessing the solubility of extraction agents before designing an experiment or process.

Under pressurized conditions, thermodynamic analysis of hydrates indicated that the addition of [BMIM]FeCl₄ alone had no noticeable effect on the stability of CO₂ hydrates. However, when combined with 3.5 wt% NaCl, it negatively impacted and altered the thermodynamic stability of the system.

In the kinetic study, both the addition of [BMIM]FeCl₄ and its combination with NaCl exhibited inhibitory effects across all aspects of the analysis:

* Amount of CO₂ in the hydrate phase (nHL): In the presence of [BMIM]FeCl₄, the quantity of CO₂ captured in the hydrate phase peaked at 0.956 mol, while with [BMIM]FeCl₄ + NaCl, it reached only 0.409 mol. These correspond to reductions by factors of 1.54 and 3.6, respectively, compared to pure CO₂ at the end of the experiment.

* Mass transfer constants (kGLa and kLHa): The gas/liquid mass transfer constant (kGLa) during pure CO₂ hydrate crystallization was recorded as 1.58·10⁻⁴ s⁻¹. Introducing [BMIM]FeCl₄ into the system reduced the transfer rate by nearly 300-fold, and when combined with NaCl, the reduction reached approximately 700-fold.

The liquid/solid transfer constant (kLHa) was determined only at the onset of nucleation. The observed values were 3.1·10⁻⁴ s⁻¹ for the pure

CO₂ system, 8.7·10⁻⁴ s⁻¹ for CO₂ + [BMIM]FeCl₄, and 5.3·10⁻⁴ s⁻¹ for CO₂ + [BMIM]FeCl₄ + NaCl. For the pure CO₂ system, the liquid/solid transfer constant (kLHa) remains close to the gas/liquid mass transfer constant, making it challenging to clearly identify the limiting step due to potential variations in accurately assessing the liquid/solid transfer. Nevertheless, for the systems including [BMIM]FeCl₄ and its combination with NaCl, the liquid/solid transfer constants (kLHa) suggest that the gas/liquid mass transfer is the rate-limiting factor.

* **Environmental Impact:** The corrosiveness of [BMIM]FeCl₄ poses a significant environmental and operational concern, particularly in its interactions with mild steel. Tests conducted under atmospheric conditions revealed that [BMIM]FeCl₄ exhibits aggressive corrosive behavior, causing substantial damage to a temperature probe within just 125 h of exposure.

### CRediT authorship contribution statement

**Angsar Serikkali:** Writing – review & editing, Writing – original draft, Methodology, Investigation. **Jérôme Douzet:** Resources, Methodology. **Jean-Michel Herri:** Supervision. **Baptiste Bouillot:** Writing – review & editing, Supervision, Project administration, Methodology, Investigation, Funding acquisition.

### Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

### Acknowledgment

The authors would like to thank the French National Research Agency (ANR) for financial support. This work is part of the INNOHYD project, funded under the French ANR-18-CE05-0006 program.

Finally, the authors would like to warmly thank Fabien Chauvy, our laboratory technician, whose help and support were invaluable throughout this work.

## Appendix A

<figure><img src="image_18.png" /><figcaption>**Fig. A1.** Liquid to solid mass transfer coefficient for CO₂ hydrate crystallization in the presence of 5v% [BMIM]FeCl₄</figcaption></figure>
<figure><img src="image_19.png" /><figcaption>Fig. A2. Liquid to solid mass transfer coefficient for CO₂ hydrate crystallization in the presence of 5v% [BMIM]FeCl₄ + 3.5 wt% NaCl</figcaption></figure>

## Appendix B

### Table B1

Initial conditions for the atmospheric reactor experiment.

[BMIM]FeCl₄ + water

<table><thead><tr><th>Reagents</th><th>m, g</th><th>n, mol</th><th>Δ abs. unc.</th></tr></thead><tbody><tr><td>[BMIM]Cl</td><td>7.1630</td><td>0.0410</td><td>0.01</td></tr><tr><td>FeCl₃·6H₂O</td><td>11.0530</td><td>0.0409</td><td>0.01</td></tr><tr><td>[BMIM]FeCl₄</td><td>13.7937</td><td>0.0409</td><td>0.0141</td></tr><tr><td>6H₂O</td><td>4.4260</td><td>0.0409</td><td>0.0141</td></tr></tbody></table>

[BMIM]FeCl₄ + water + 2 wt% NaCl

<table><thead><tr><th>Reagents</th><th>m, g</th><th>n, mol</th><th>Δ abs. unc.</th></tr></thead><tbody><tr><td>[BMIM]Cl</td><td>7.1660</td><td>0.0410</td><td>0.01</td></tr><tr><td>FeCl₃·6H₂O</td><td>11.0730</td><td>0.0410</td><td>0.01</td></tr><tr><td>[BMIM]FeCl₄</td><td>13.8091</td><td>0.0410</td><td>0.0141</td></tr><tr><td>6H₂O</td><td>4.4309</td><td>0.0410</td><td>0.0141</td></tr></tbody></table>

[BMIM]FeCl₄ + water + 12–14 wt% NaCl

<table><thead><tr><th>Reagents</th><th>m, g</th><th>n, mol</th><th>Δ abs. unc.</th></tr></thead><tbody><tr><td>[BMIM]Cl</td><td>7.1620</td><td>0.0410</td><td>0.01</td></tr><tr><td>FeCl₃·6H₂O</td><td>11.0720</td><td>0.0410</td><td>0.01</td></tr><tr><td>[BMIM]FeCl₄</td><td>13.8046</td><td>0.0410</td><td>0.0141</td></tr><tr><td>6H₂O</td><td>4.4295</td><td>0.0410</td><td>0.0141</td></tr></tbody></table>

### Table B2

Documented results for atmospheric reactor experiment 1.

IL + H₂O

<table><thead><tr><th colspan="6">Experiment 1</th><th colspan="4">Water addition</th></tr><tr><th>Number</th><th colspan="3">Inside the vessel</th><th colspan="2">Solution, g</th><th>H₂O, g</th><th>Weighed, g</th><th>Left, g</th><th>T, °C</th></tr><tr><th></th><th>H₂O, g</th><th>IL, g</th><th>IL, wt%</th><th>H₂O, wt%</th><th>Solution, g</th><th></th><th></th><th></th><th></th></tr></thead><tbody><tr><td>0</td><td>4.43</td><td>13.8</td><td>75.72</td><td>24.28</td><td>18.22</td><td>0</td><td>0</td><td>0</td><td>7.67</td></tr><tr><td>1</td><td>25.68</td><td>13.81</td><td>34.97</td><td>65.03</td><td>39.47</td><td>21.25</td><td>21.32</td><td>0.07</td><td>7.67</td></tr><tr><td>2</td><td>25.95</td><td>13.81</td><td>34.73</td><td>65.27</td><td>39.74</td><td>0.28</td><td>0.34</td><td>0.06</td><td>7.67</td></tr><tr><td>3</td><td>26.23</td><td>13.81</td><td>34.49</td><td>65.51</td><td>40.02</td><td>0.28</td><td>0.31</td><td>0.03</td><td>7.67</td></tr><tr><td>4</td><td>26.53</td><td>13.81</td><td>34.23</td><td>65.77</td><td>40.32</td><td>0.3</td><td>0.34</td><td>0.04</td><td>7.67</td></tr><tr><td>5</td><td>26.77</td><td>13.81</td><td>34.03</td><td>65.97</td><td>40.56</td><td>0.24</td><td>0.26</td><td>0.02</td><td>9.23</td></tr><tr><td>6</td><td>27.09</td><td>13.81</td><td>33.77</td><td>66.23</td><td>40.88</td><td>0.32</td><td>0.36</td><td>0.05</td><td>9.23</td></tr><tr><td>7</td><td>27.42</td><td>13.81</td><td>33.5</td><td>66.5</td><td>41.21</td><td>0.33</td><td>0.35</td><td>0.01</td><td>10.8</td></tr><tr><td>8</td><td>27.7</td><td>13.81</td><td>33.27</td><td>66.73</td><td>41.49</td><td>0.28</td><td>0.3</td><td>0.01</td><td>10.8</td></tr><tr><td>9</td><td>27.98</td><td>13.81</td><td>33.05</td><td>66.95</td><td>41.77</td><td>0.28</td><td>0.3</td><td>0.02</td><td>12.37</td></tr><tr><td>10</td><td>28.27</td><td>13.81</td><td>32.82</td><td>67.18</td><td>42.06</td><td>0.29</td><td>0.32</td><td>0.03</td><td>12.37</td></tr></tbody></table>

(continued on next page)
<table><caption>**Table B2 (continued)**</caption><caption>IL + H<sub>2</sub>O</caption><thead><tr><th rowspan="2">Experiment 1<br>Number</th><th colspan="4">Inside the vessel</th><th colspan="2">Water addition</th><th rowspan="2">Left, g</th><th rowspan="2">T, °C</th></tr><tr><th>H<sub>2</sub>O, g</th><th>IL, g</th><th>IL, wt%</th><th>H<sub>2</sub>O, wt%</th><th>Solution, g</th><th>H<sub>2</sub>O, g</th><th>Weighed, g</th></tr></thead><tbody><tr><td>11</td><td>28.64</td><td>13.81</td><td>32.53</td><td>67.47</td><td>42.43</td><td>0.37</td><td>0.42</td><td>0.05</td><td>14.35</td></tr><tr><td>12</td><td>28.91</td><td>13.81</td><td>32.33</td><td>67.67</td><td>42.7</td><td>0.27</td><td>0.3</td><td>0.03</td><td>16.35</td></tr><tr><td><b>13</b></td><td><b>29.2</b></td><td><b>13.81</b></td><td><b>32.11</b></td><td><b>67.89</b></td><td><b>42.99</b></td><td><b>0.29</b></td><td><b>0.34</b></td><td><b>0.04</b></td><td><b>16.35</b></td></tr><tr><td>14</td><td>29.49</td><td>13.81</td><td>31.89</td><td>68.11</td><td>43.28</td><td>0.29</td><td>0.32</td><td>0.03</td><td>18.18</td></tr><tr><td>15</td><td>29.78</td><td>13.81</td><td>31.68</td><td>68.32</td><td>43.57</td><td>0.29</td><td>0.32</td><td>0.03</td><td>18.18</td></tr><tr><td><b>16</b></td><td><b>30.1</b></td><td><b>13.81</b></td><td><b>31.45</b></td><td><b>68.55</b></td><td><b>43.89</b></td><td><b>0.32</b></td><td><b>0.33</b></td><td><b>0.01</b></td><td><b>20</b></td></tr></tbody></table>

IL = [BMIM]FeCl₄.

Bold markings are used to indicate saturation points.

<caption>**Table B3**</caption>

Absolute and relative uncertainties for atmospheric reactor experiment 1.

<table><caption>IL + H<sub>2</sub>O</caption><thead><tr><th rowspan="2">Experiment 1<br>Number</th><th colspan="4">ΔInside the vessel ±</th><th colspan="2">ΔWater addition ±</th><th rowspan="2">Left, g</th><th rowspan="2">T, °C</th></tr><tr><th>H<sub>2</sub>O, g</th><th>IL, g</th><th>IL, wt%</th><th>H<sub>2</sub>O, wt%</th><th>Solution, g</th><th>H<sub>2</sub>O, g</th><th>Weighed, g</th></tr></thead><tbody><tr><td>0</td><td>0.014</td><td>0.014</td><td>0.097</td><td>0.08</td><td>0.014</td><td></td><td></td><td>7.67</td></tr><tr><td>1</td><td>0.02</td><td>0.014</td><td>0.04</td><td>0.06</td><td>0.02</td><td>0.01</td><td>0.01</td><td>7.67</td></tr><tr><td>2</td><td>0.024</td><td>0.014</td><td>0.042</td><td>0.074</td><td>0.024</td><td>0.01</td><td>0.01</td><td>7.67</td></tr><tr><td>3</td><td>0.028</td><td>0.014</td><td>0.043</td><td>0.084</td><td>0.028</td><td>0.01</td><td>0.01</td><td>7.67</td></tr><tr><td><b>4</b></td><td><b>0.032</b></td><td><b>0.014</b></td><td><b>0.044</b></td><td><b>0.094</b></td><td><b>0.032</b></td><td><b>0.01</b></td><td><b>0.01</b></td><td><b>7.67</b></td></tr><tr><td>5</td><td>0.035</td><td>0.014</td><td>0.045</td><td>0.102</td><td>0.035</td><td>0.01</td><td>0.01</td><td>9.23</td></tr><tr><td><b>6</b></td><td><b>0.037</b></td><td><b>0.014</b></td><td><b>0.046</b></td><td><b>0.11</b></td><td><b>0.037</b></td><td><b>0.01</b></td><td><b>0.01</b></td><td><b>9.23</b></td></tr><tr><td>7</td><td>0.04</td><td>0.014</td><td>0.047</td><td>0.117</td><td>0.04</td><td>0.01</td><td>0.01</td><td>10.8</td></tr><tr><td><b>8</b></td><td><b>0.042</b></td><td><b>0.014</b></td><td><b>0.048</b></td><td><b>0.123</b></td><td><b>0.042</b></td><td><b>0.01</b></td><td><b>0.01</b></td><td><b>10.82</b></td></tr><tr><td>9</td><td>0.045</td><td>0.014</td><td>0.049</td><td>0.129</td><td>0.045</td><td>0.01</td><td>0.01</td><td>12.37</td></tr><tr><td><b>10</b></td><td><b>0.047</b></td><td><b>0.014</b></td><td><b>0.05</b></td><td><b>0.134</b></td><td><b>0.047</b></td><td><b>0.01</b></td><td><b>0.01</b></td><td><b>12.37</b></td></tr><tr><td>11</td><td>0.049</td><td>0.014</td><td>0.05</td><td>0.139</td><td>0.049</td><td>0.01</td><td>0.01</td><td>14.35</td></tr><tr><td>12</td><td>0.051</td><td>0.014</td><td>0.051</td><td>0.144</td><td>0.051</td><td>0.01</td><td>0.01</td><td>16.35</td></tr><tr><td><b>13</b></td><td><b>0.053</b></td><td><b>0.014</b></td><td><b>0.051</b></td><td><b>0.149</b></td><td><b>0.053</b></td><td><b>0.01</b></td><td><b>0.01</b></td><td><b>16.35</b></td></tr><tr><td>14</td><td>0.055</td><td>0.014</td><td>0.052</td><td>0.153</td><td>0.055</td><td>0.01</td><td>0.01</td><td>18.18</td></tr><tr><td>15</td><td>0.057</td><td>0.014</td><td>0.052</td><td>0.157</td><td>0.057</td><td>0.01</td><td>0.01</td><td>18.18</td></tr><tr><td><b>16</b></td><td><b>0.058</b></td><td><b>0.014</b></td><td><b>0.053</b></td><td><b>0.161</b></td><td><b>0.058</b></td><td><b>0.01</b></td><td><b>0.01</b></td><td><b>20</b></td></tr></tbody></table>

IL = [BMIM]FeCl₄.

Bold markings are used to indicate saturation points.

<caption>**Table B4**</caption>

Documented results for atmospheric reactor experiment 2.

<table><caption>[BMIM]FeCl<sub>4</sub> + H<sub>2</sub>O + 2 wt% NaCl</caption><thead><tr><th rowspan="2">Experiment 2<br>Number</th><th colspan="4">Inside the vessel</th><th colspan="2">Solution addition</th><th rowspan="2">Weighed, g</th><th rowspan="2">Left, g</th><th rowspan="2">Temp, C</th></tr><tr><th>H<sub>2</sub>O, g</th><th>IL, g</th><th>IL, wt%</th><th>H<sub>2</sub>O, wt%</th><th>Solution, g</th><th>NaCl, g</th><th>NaCl, wt%</th></tr></thead><tbody><tr><td>0</td><td>4.4309</td><td>13.8</td><td>75.6873</td><td>24.2983</td><td>18.239</td><td>0</td><td>0</td><td>0.665</td><td>18.35</td><td>19.012</td><td>19.054</td><td>0.042</td><td>7.47</td></tr><tr><td>1</td><td>22.778</td><td>13.81</td><td>37.0704</td><td>61.1444</td><td>37.251</td><td>0.6654</td><td>1.7863</td><td>0.106</td><td>2.912</td><td>3.018</td><td>3.053</td><td>0.035</td><td>7.5</td></tr><tr><td>2</td><td>25.69</td><td>13.81</td><td>34.2921</td><td>63.7941</td><td>40.269</td><td>0.7711</td><td>1.9147</td><td>0.071</td><td>1.969</td><td>2.04</td><td>2.093</td><td>0.053</td><td>7.5</td></tr><tr><td>3</td><td>27.658</td><td>13.81</td><td>32.6386</td><td>65.3710</td><td>42.309</td><td>0.8425</td><td>1.9912</td><td>0.043</td><td>1.172</td><td>1.215</td><td>1.247</td><td>0.032</td><td>7.5</td></tr><tr><td>4</td><td>28.831</td><td>13.81</td><td>31.7275</td><td>66.2400</td><td>43.524</td><td>0.8850</td><td>2.0333</td><td>0.011</td><td>0.304</td><td>0.315</td><td>0.374</td><td>0.059</td><td>7.6</td></tr><tr><td>5</td><td>29.135</td><td>13.81</td><td>31.4995</td><td>66.4574</td><td>43.839</td><td>0.8960</td><td>2.0438</td><td>0.01</td><td>0.266</td><td>0.276</td><td>0.288</td><td>0.012</td><td>7.6</td></tr><tr><td>6</td><td>29.401</td><td>13.81</td><td>31.3025</td><td>66.6453</td><td>44.115</td><td>0.9057</td><td>2.0530</td><td>0.01</td><td>0.362</td><td>0.375</td><td>0.386</td><td>0.011</td><td>7.6</td></tr><tr><td>7</td><td>29.763</td><td>13.81</td><td>31.0386</td><td>66.8970</td><td>44.49</td><td>0.9188</td><td>2.0651</td><td>0.013</td><td>0.362</td><td>0.375</td><td>0.386</td><td>0.011</td><td>7.6</td></tr><tr><td><b>8</b></td><td><b>30.252</b></td><td><b>13.81</b></td><td><b>30.6889</b></td><td><b>67.2305</b></td><td><b>44.997</b></td><td><b>0.9365</b></td><td><b>2.0813</b></td><td><b>0.018</b></td><td><b>0.489</b></td><td><b>0.507</b></td><td><b>0.521</b></td><td><b>0.014</b></td><td><b>7.6</b></td></tr><tr><td>9</td><td>30.548</td><td>13.81</td><td>30.4816</td><td>67.4282</td><td>45.303</td><td>0.9472</td><td>2.0909</td><td>0.011</td><td>0.295</td><td>0.306</td><td>0.317</td><td>0.011</td><td>9.5</td></tr><tr><td>10</td><td>30.899</td><td>13.81</td><td>30.2386</td><td>67.6599</td><td>45.667</td><td>0.9600</td><td>2.1021</td><td>0.013</td><td>0.351</td><td>0.364</td><td>0.38</td><td>0.016</td><td>9.43</td></tr><tr><td><b>11</b></td><td><b>31.188</b></td><td><b>13.81</b></td><td><b>30.0413</b></td><td><b>67.8482</b></td><td><b>45.967</b></td><td><b>0.9705</b></td><td><b>2.1113</b></td><td><b>0.011</b></td><td><b>0.29</b></td><td><b>0.3</b></td><td><b>0.316</b></td><td><b>0.016</b></td><td><b>9.49</b></td></tr><tr><td>12</td><td>31.487</td><td>13.81</td><td>29.8407</td><td>68.0395</td><td>46.276</td><td>0.9813</td><td>2.1205</td><td>0.011</td><td>0.298</td><td>0.309</td><td>0.32</td><td>0.011</td><td>11.27</td></tr><tr><td>13</td><td>31.818</td><td>13.81</td><td>29.6211</td><td>68.2489</td><td>46.619</td><td>0.9933</td><td>2.1307</td><td>0.012</td><td>0.331</td><td>0.343</td><td>0.355</td><td>0.012</td><td>11.3</td></tr><tr><td><b>14</b></td><td><b>31.997</b></td><td><b>13.81</b></td><td><b>29.5034</b></td><td><b>68.3611</b></td><td><b>46.805</b></td><td><b>0.9998</b></td><td><b>2.1361</b></td><td><b>0.007</b></td><td><b>0.179</b></td><td><b>0.186</b></td><td><b>0.199</b></td><td><b>0.013</b></td><td><b>11.24</b></td></tr><tr><td>15</td><td>32.194</td><td>13.81</td><td>29.3754</td><td>68.4832</td><td>47.009</td><td>1.0070</td><td>2.1420</td><td>0.007</td><td>0.197</td><td>0.204</td><td>0.215</td><td>0.011</td><td>13.14</td></tr><tr><td>16</td><td>32.427</td><td>13.81</td><td>29.2256</td><td>68.6261</td><td>47.25</td><td>1.0154</td><td>2.1490</td><td>0.008</td><td>0.233</td><td>0.241</td><td>0.254</td><td>0.013</td><td>13</td></tr><tr><td>17</td><td>32.62</td><td>13.81</td><td>29.1024</td><td>68.7436</td><td>47.45</td><td>1.0224</td><td>2.1547</td><td>0.007</td><td>0.193</td><td>0.2</td><td>0.213</td><td>0.013</td><td>13</td></tr><tr><td><b>18</b></td><td><b>32.947</b></td><td><b>13.81</b></td><td><b>28.8959</b></td><td><b>68.9405</b></td><td><b>47.789</b></td><td><b>1.0343</b></td><td><b>2.1642</b></td><td><b>0.012</b></td><td><b>0.327</b></td><td><b>0.339</b></td><td><b>0.352</b></td><td><b>0.013</b></td><td><b>13.14</b></td></tr><tr><td><b>19</b></td><td><b>33.124</b></td><td><b>13.81</b></td><td><b>28.7851</b></td><td><b>69.0462</b></td><td><b>47.973</b></td><td><b>1.0407</b></td><td><b>2.1693</b></td><td><b>0.006</b></td><td><b>0.178</b></td><td><b>0.184</b></td><td><b>0.196</b></td><td><b>0.012</b></td><td><b>14.9</b></td></tr><tr><td>20</td><td>33.438</td><td>13.81</td><td>28.5914</td><td>69.2309</td><td>48.298</td><td>1.0521</td><td>2.1783</td><td>0.011</td><td>0.314</td><td>0.325</td><td>0.339</td><td>0.014</td><td>18.49</td></tr><tr><td>21</td><td>33.805</td><td>13.81</td><td>28.3682</td><td>69.4438</td><td>48.678</td><td>1.0654</td><td>2.1886</td><td>0.013</td><td>0.367</td><td>0.38</td><td>0.421</td><td>0.041</td><td>18.54</td></tr></tbody></table>

(continued on next page)
<table><caption>**Table B4 (continued)**</caption><caption>[BMIM]FeCl<sub>4</sub> + H<sub>2</sub>O + 2 wt% NaCl</caption><thead><tr><th colspan="9">Experiment 2</th><th colspan="7">Solution addition</th></tr><tr><th>Number</th><th colspan="4">Inside the vessel</th><th colspan="2">Solution, g</th><th>NaCl, g</th><th>NaCl, wt%</th><th>NaCl, g</th><th>H<sub>2</sub>O, g</th><th>Solution, g</th><th>Weighed, g</th><th>Left, g</th><th>Temp, C</th></tr><tr><th></th><th>H<sub>2</sub>O, g</th><th>IL, g</th><th>IL, wt%</th><th>H<sub>2</sub>O, wt%</th><th>Solution, g</th><th>NaCl, g</th><th>NaCl, wt%</th><th></th><th></th><th></th><th></th><th></th><th></th><th></th></tr></thead><tbody><tr><td>22</td><td>34.129</td><td>13.81</td><td>28.1737</td><td>69.6293</td><td>49.014</td><td>1.0771</td><td>2.1976</td><td>0.012</td><td>0.324</td><td>0.336</td><td>0.346</td><td>0.01</td><td>18.58</td></tr><tr><td>23</td><td>34.466</td><td>13.81</td><td>27.9746</td><td>69.8193</td><td>49.363</td><td>1.0893</td><td>2.2068</td><td>0.012</td><td>0.337</td><td>0.349</td><td>0.36</td><td>0.011</td><td>20.36</td></tr><tr><td>24</td><td>34.718</td><td>13.81</td><td>27.8269</td><td>69.9601</td><td>49.625</td><td>1.0985</td><td>2.2136</td><td>0.009</td><td>0.253</td><td>0.262</td><td>0.276</td><td>0.014</td><td>20.38</td></tr><tr><td>25</td><td>34.976</td><td>13.81</td><td>27.6779</td><td>70.1022</td><td>49.892</td><td>1.1079</td><td>2.2205</td><td>0.009</td><td>0.258</td><td>0.267</td><td>0.279</td><td>0.012</td><td>20.41</td></tr><tr><td>26</td><td>35.211</td><td>13.81</td><td>27.5438</td><td>70.2301</td><td>50.135</td><td>1.1164</td><td>2.2267</td><td>0.009</td><td>0.234</td><td>0.243</td><td>0.255</td><td>0.012</td><td>20.38</td></tr></tbody></table>

IL = [BMIM]FeCl₄.

Bold markings are used to indicate saturation points.

<caption>**Table B5**</caption>

Absolute and relative uncertainties for atmospheric reactor experiment 2.

<table><caption>[BMIM]FeCl<sub>4</sub> + H<sub>2</sub>O + 2 wt% NaCl</caption><thead><tr><th colspan="9">Experiment 2</th><th colspan="7">ΔSolution addition ±</th></tr><tr><th>Number</th><th colspan="4">ΔInside the vessel ±</th><th colspan="2">Solution, g</th><th>NaCl, g</th><th>NaCl, wt%</th><th>NaCl, g</th><th>H<sub>2</sub>O, g</th><th>Solution, g</th><th>Weighed, g</th><th>Left, g</th><th>Temp, C</th></tr><tr><th></th><th>H<sub>2</sub>O, g</th><th>IL, g</th><th>IL, wt%</th><th>H<sub>2</sub>O, wt%</th><th>Solution, g</th><th>NaCl, g</th><th>NaCl, wt%</th><th></th><th></th><th></th><th></th><th></th><th></th><th></th></tr></thead><tbody><tr><td>0</td><td>0.0141</td><td>0.014</td><td>0.0972</td><td>7.9808</td><td>0.0141</td><td>0.0000</td><td>0.0000</td><td>0.0000</td><td>0.0006</td><td>0.0142</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>7.47</td></tr><tr><td>1</td><td>0.02</td><td>0.014</td><td>4.2865</td><td>6.2952</td><td>0.0200</td><td>0.0006</td><td>0.1931</td><td>0.0006</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>7.5</td></tr><tr><td>2</td><td>0.0245</td><td>0.014</td><td>4.0847</td><td>7.2178</td><td>0.0245</td><td>0.0008</td><td>0.2301</td><td>0.0005</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>7.5</td></tr><tr><td>3</td><td>0.0283</td><td>0.014</td><td>3.9917</td><td>7.9898</td><td>0.0283</td><td>0.0009</td><td>0.2592</td><td>0.0005</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>7.5</td></tr><tr><td>4</td><td>0.0316</td><td>0.014</td><td>3.9839</td><td>8.7183</td><td>0.0316</td><td>0.0011</td><td>0.2855</td><td>0.0005</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>7.5</td></tr><tr><td>5</td><td>0.0347</td><td>0.014</td><td>4.0746</td><td>9.4913</td><td>0.0346</td><td>0.0012</td><td>0.3125</td><td>0.0005</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>7.6</td></tr><tr><td>6</td><td>0.0374</td><td>0.014</td><td>4.1624</td><td>10.1965</td><td>0.0374</td><td>0.0013</td><td>0.3370</td><td>0.0005</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>7.6</td></tr><tr><td>7</td><td>0.04</td><td>0.014</td><td>4.2299</td><td>10.8213</td><td>0.0400</td><td>0.0014</td><td>0.3588</td><td>0.0005</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>7.6</td></tr><tr><td>8</td><td>0.0425</td><td>0.014</td><td>4.2721</td><td>11.3659</td><td>0.0424</td><td>0.0015</td><td>0.3778</td><td>0.0005</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>7.6</td></tr><tr><td>9</td><td>0.0447</td><td>0.014</td><td>4.3358</td><td>11.9107</td><td>0.0447</td><td>0.0015</td><td>0.3967</td><td>0.0005</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>9.5</td></tr><tr><td>10</td><td>0.0469</td><td>0.014</td><td>4.3859</td><td>12.4058</td><td>0.0469</td><td>0.0016</td><td>0.4139</td><td>0.0005</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>9.43</td></tr><tr><td>11</td><td>0.049</td><td>0.014</td><td>4.4403</td><td>12.8841</td><td>0.0490</td><td>0.0017</td><td>0.4305</td><td>0.0005</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>9.49</td></tr><tr><td>12</td><td>0.051</td><td>0.014</td><td>4.4890</td><td>13.3326</td><td>0.0510</td><td>0.0018</td><td>0.4460</td><td>0.0005</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>11.27</td></tr><tr><td>13</td><td>0.0529</td><td>0.014</td><td>4.5284</td><td>13.7474</td><td>0.0529</td><td>0.0018</td><td>0.4604</td><td>0.0005</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>11.3</td></tr><tr><td>14</td><td>0.0548</td><td>0.014</td><td>4.5880</td><td>14.1808</td><td>0.0548</td><td>0.0019</td><td>0.4753</td><td>0.0005</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>11.24</td></tr><tr><td>15</td><td>0.0566</td><td>0.014</td><td>4.6418</td><td>14.5906</td><td>0.0566</td><td>0.0020</td><td>0.4895</td><td>0.0005</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>13.14</td></tr><tr><td>16</td><td>0.0583</td><td>0.014</td><td>4.6868</td><td>14.9730</td><td>0.0583</td><td>0.0020</td><td>0.5027</td><td>0.0005</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>13</td></tr><tr><td>17</td><td>0.06</td><td>0.014</td><td>4.7355</td><td>15.3505</td><td>0.0600</td><td>0.0021</td><td>0.5157</td><td>0.0005</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>13</td></tr><tr><td>18</td><td>0.0617</td><td>0.014</td><td>4.7593</td><td>15.6737</td><td>0.0616</td><td>0.0021</td><td>0.5269</td><td>0.0005</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>13.14</td></tr><tr><td>19</td><td>0.0633</td><td>0.014</td><td>4.8054</td><td>16.0271</td><td>0.0632</td><td>0.0022</td><td>0.5391</td><td>0.0005</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>14.9</td></tr><tr><td>20</td><td>0.0648</td><td>0.014</td><td>4.8262</td><td>16.3265</td><td>0.0648</td><td>0.0022</td><td>0.5495</td><td>0.0005</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>18.49</td></tr><tr><td>21</td><td>0.0664</td><td>0.014</td><td>4.8357</td><td>16.5968</td><td>0.0663</td><td>0.0023</td><td>0.5590</td><td>0.0005</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>18.54</td></tr><tr><td>22</td><td>0.0679</td><td>0.014</td><td>4.8501</td><td>16.8681</td><td>0.0678</td><td>0.0024</td><td>0.5684</td><td>0.0005</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>18.58</td></tr><tr><td>23</td><td>0.0693</td><td>0.014</td><td>4.8604</td><td>17.1243</td><td>0.0693</td><td>0.0024</td><td>0.5774</td><td>0.0005</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>20.36</td></tr><tr><td>24</td><td>0.0708</td><td>0.014</td><td>4.8829</td><td>17.3967</td><td>0.0707</td><td>0.0025</td><td>0.5869</td><td>0.0005</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>20.38</td></tr><tr><td>25</td><td>0.0722</td><td>0.014</td><td>4.9029</td><td>17.6580</td><td>0.0721</td><td>0.0025</td><td>0.5959</td><td>0.0005</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>20.41</td></tr><tr><td>26</td><td>0.0735</td><td>0.014</td><td>4.9250</td><td>17.9180</td><td>0.0735</td><td>0.0026</td><td>0.6050</td><td>0.0005</td><td>0.0142</td><td>0.0141</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>20.38</td></tr></tbody></table>

IL = [BMIM]FeCl₄.

Bold markings are used to indicate saturation points.

<caption>**Table B6**</caption>

Documented results for atmospheric reactor experiment 3.

<table><caption>[BMIM]FeCl<sub>4</sub> + H<sub>2</sub>O + 12–14 wt% NaCl</caption><thead><tr><th colspan="9">Experiment 3</th><th colspan="7">Solution addition</th></tr><tr><th>Number</th><th colspan="4">Inside the vessel</th><th colspan="2">Solution, g</th><th>NaCl, g</th><th>NaCl, wt%</th><th>NaCl, g</th><th>H<sub>2</sub>O, g</th><th>Solution, g</th><th>Weighed, g</th><th>Left, g</th><th>Temp, C</th></tr><tr><th></th><th>H<sub>2</sub>O, g</th><th>IL, g</th><th>IL, wt%</th><th>H<sub>2</sub>O, wt%</th><th>Solution, g</th><th>NaCl, g</th><th>NaCl, wt%</th><th></th><th></th><th></th><th></th><th></th><th></th><th></th></tr></thead><tbody><tr><td>0</td><td>4.4295</td><td>13.8</td><td>75.7080</td><td>24.2924</td><td>18.2340</td><td>0.0000</td><td>0.0000</td><td>0.0000</td><td>3.4102</td><td>15.6958</td><td>19.106</td><td>0</td><td>0</td><td>7.47</td></tr><tr><td>1</td><td>20.125</td><td>13.81</td><td>36.9820</td><td>53.8909</td><td>37.3400</td><td>3.4102</td><td>9.1327</td><td>3.4102</td><td>15.6958</td><td>19.106</td><td>19.148</td><td>0.042</td><td>0.042</td><td>7.63</td></tr><tr><td>2</td><td>22.438</td><td>13.81</td><td>34.3894</td><td>55.8718</td><td>40.1550</td><td>3.9126</td><td>9.7437</td><td>0.5024</td><td>2.3126</td><td>2.815</td><td>2.857</td><td>0.042</td><td>0.042</td><td>7.5</td></tr><tr><td>3</td><td>23.314</td><td>13.81</td><td>33.5001</td><td>56.5514</td><td>41.2210</td><td>4.1029</td><td>9.9533</td><td>0.1903</td><td>0.8757</td><td>1.066</td><td>1.078</td><td>0.012</td><td>0.012</td><td>7.6</td></tr><tr><td>4</td><td>25.099</td><td>13.81</td><td>31.8226</td><td>57.8332</td><td>43.3940</td><td>4.4907</td><td>10.3487</td><td>0.3879</td><td>1.7851</td><td>2.173</td><td>2.189</td><td>0.016</td><td>0.016</td><td>7.58</td></tr><tr><td>5</td><td>27.159</td><td>13.81</td><td>30.0838</td><td>59.1618</td><td>45.9020</td><td>4.9384</td><td>10.7585</td><td>0.4476</td><td>2.0604</td><td>2.508</td><td>2.535</td><td>0.027</td><td>0.027</td><td>7.6</td></tr><tr><td>6</td><td>27.966</td><td>13.81</td><td>29.4537</td><td>59.6432</td><td>46.8840</td><td>5.1136</td><td>10.9070</td><td>0.1753</td><td>0.8067</td><td>0.982</td><td>1.015</td><td>0.033</td><td>0.033</td><td>7.6</td></tr><tr><td>7</td><td>29.599</td><td>13.81</td><td>28.2556</td><td>60.5587</td><td>48.8720</td><td>5.4685</td><td>11.1894</td><td>0.3548</td><td>1.6332</td><td>1.988</td><td>2.004</td><td>0.016</td><td>0.016</td><td>7.61</td></tr><tr><td>8</td><td>31.625</td><td>13.81</td><td>26.8984</td><td>61.5958</td><td>51.3380</td><td>5.9086</td><td>11.5092</td><td>0.4401</td><td>2.0259</td><td>2.466</td><td>2.532</td><td>0.066</td><td>0.066</td><td>7.6</td></tr><tr><td>9</td><td>32.125</td><td>13.81</td><td>26.5830</td><td>61.8368</td><td>51.9470</td><td>6.0173</td><td>11.5835</td><td>0.1087</td><td>0.5003</td><td>0.609</td><td>0.624</td><td>0.015</td><td>0.015</td><td>7.6</td></tr><tr><td>10</td><td>32.557</td><td>13.81</td><td>26.3165</td><td>62.0404</td><td>52.4730</td><td>6.1112</td><td>11.6464</td><td>0.0939</td><td>0.4321</td><td>0.526</td><td>0.543</td><td>0.017</td><td>0.017</td><td>7.6</td></tr><tr><td>11</td><td>33.055</td><td>13.81</td><td>26.0161</td><td>62.2700</td><td>53.0790</td><td>6.2194</td><td>11.7172</td><td>0.1082</td><td>0.4978</td><td>0.606</td><td>0.624</td><td>0.018</td><td>0.018</td><td>7.6</td></tr><tr><td>12</td><td>33.453</td><td>13.81</td><td>25.7810</td><td>62.4496</td><td>53.5630</td><td>6.3057</td><td>11.7726</td><td>0.0864</td><td>0.3976</td><td>0.484</td><td>0.508</td><td>0.024</td><td>0.024</td><td>7.33</td></tr><tr><td>13</td><td>33.946</td><td>13.81</td><td>25.4954</td><td>62.6679</td><td>54.1630</td><td>6.4128</td><td>11.8399</td><td>0.1071</td><td>0.4929</td><td>0.6</td><td>0.629</td><td>0.029</td><td>0.029</td><td>7.38</td></tr><tr><td>14</td><td>34.269</td><td>13.81</td><td>25.3118</td><td>62.8082</td><td>54.5560</td><td>6.4830</td><td>11.8832</td><td>0.0701</td><td>0.3229</td><td>0.393</td><td>0.405</td><td>0.012</td><td>0.012</td><td>7.47</td></tr></tbody></table>

(continued on next page)
<table><caption>Table B6 (continued)</caption><caption>[BMIM]FeCl<sub>4</sub> + H<sub>2</sub>O + 12–14 wt% NaCl</caption><thead><tr><th colspan="10">Experiment 3</th><th colspan="7">Inside the vessel</th><th colspan="7">Solution addition</th></tr><tr><th>Number</th><th>H<sub>2</sub>O, g</th><th>IL, g</th><th>IL, wt%</th><th>H<sub>2</sub>O, wt %</th><th>Solution, g</th><th>NaCl, g</th><th>NaCl, wt %</th><th>NaCl, g</th><th>H<sub>2</sub>O, g</th><th>Solution, g</th><th>Weighed, g</th><th>Left, g</th><th>Temp, C</th></tr></thead><tbody><tr><td>15</td><td>34.665</td><td>13.81</td><td>25.0896</td><td>62.9779</td><td>55.0390</td><td>6.5692</td><td>11.9355</td><td>0.0862</td><td>0.3968</td><td>0.483</td><td>0.504</td><td>0.021</td><td>7.47</td></tr><tr><td>16</td><td>35.06</td><td>13.81</td><td>24.8723</td><td>63.1440</td><td>55.5200</td><td>6.6550</td><td>11.9867</td><td>0.0859</td><td>0.3951</td><td>0.481</td><td>0.489</td><td>0.008</td><td>7.5</td></tr><tr><td><b>17</b></td><td><b>35.312</b></td><td><b>13.81</b></td><td><b>24.7359</b></td><td><b>63.2482</b></td><td><b>55.8260</b></td><td><b>6.7097</b></td><td><b>12.0189</b></td><td><b>0.0546</b></td><td><b>0.2514</b></td><td><b>0.306</b></td><td><b>0.358</b></td><td><b>0.052</b></td><td><b>7.5</b></td></tr><tr><td>18</td><td>35.606</td><td>13.81</td><td>24.5783</td><td>63.3686</td><td>56.1840</td><td>6.7736</td><td>12.0560</td><td>0.0639</td><td>0.2941</td><td>0.358</td><td>0.375</td><td>0.017</td><td>9.3</td></tr><tr><td>19</td><td>35.855</td><td>13.81</td><td>24.4465</td><td>63.4694</td><td>56.4870</td><td>6.8276</td><td>12.0871</td><td>0.0541</td><td>0.2489</td><td>0.303</td><td>0.322</td><td>0.019</td><td>9.3</td></tr><tr><td>20</td><td>36.069</td><td>13.81</td><td>24.3340</td><td>63.5553</td><td>56.7480</td><td>6.8742</td><td>12.1136</td><td>0.0466</td><td>0.2144</td><td>0.261</td><td>0.281</td><td>0.02</td><td>9.3</td></tr><tr><td>21</td><td>36.271</td><td>13.81</td><td>24.2290</td><td>63.6356</td><td>56.9940</td><td>6.9181</td><td>12.1383</td><td>0.0439</td><td>0.2021</td><td>0.246</td><td>0.327</td><td>0.081</td><td>9.29</td></tr><tr><td>22</td><td>36.482</td><td>13.81</td><td>24.1202</td><td>63.7187</td><td>57.2510</td><td>6.9640</td><td>12.1640</td><td>0.0459</td><td>0.2111</td><td>0.257</td><td>0.279</td><td>0.022</td><td>9.29</td></tr><tr><td>23</td><td>36.681</td><td>13.81</td><td>24.0187</td><td>63.7963</td><td>57.4930</td><td>7.0072</td><td>12.1879</td><td>0.0432</td><td>0.1988</td><td>0.242</td><td>0.256</td><td>0.014</td><td>9.3</td></tr><tr><td><b>24</b></td><td><b>36.863</b></td><td><b>13.81</b></td><td><b>23.9267</b></td><td><b>63.8665</b></td><td><b>57.7140</b></td><td><b>7.0466</b></td><td><b>12.2096</b></td><td><b>0.0394</b></td><td><b>0.1816</b></td><td><b>0.221</b></td><td><b>0.232</b></td><td><b>0.011</b></td><td><b>9.3</b></td></tr><tr><td>25</td><td>37.335</td><td>13.81</td><td>23.6907</td><td>64.0469</td><td>58.2890</td><td>7.1493</td><td>12.2652</td><td>0.1026</td><td>0.4724</td><td>0.575</td><td>0.596</td><td>0.021</td><td>11.2</td></tr><tr><td>26</td><td>37.77</td><td>13.81</td><td>23.4776</td><td>64.2097</td><td>58.8180</td><td>7.2437</td><td>12.3154</td><td>0.0944</td><td>0.4346</td><td>0.529</td><td>0.551</td><td>0.022</td><td>11.14</td></tr><tr><td>27</td><td>38.073</td><td>13.81</td><td>23.3314</td><td>64.3215</td><td>59.1867</td><td>7.3095</td><td>12.3499</td><td>0.0658</td><td>0.3029</td><td>0.3687</td><td>0.38</td><td>0.0113</td><td>11.14</td></tr><tr><td>28</td><td>38.393</td><td>13.81</td><td>23.1787</td><td>64.4382</td><td>59.5767</td><td>7.3791</td><td>12.3859</td><td>0.0696</td><td>0.3204</td><td>0.39</td><td>0.403</td><td>0.013</td><td>11.14</td></tr><tr><td>29</td><td>38.677</td><td>13.81</td><td>23.0452</td><td>64.5402</td><td>59.9217</td><td>7.4407</td><td>12.4173</td><td>0.0616</td><td>0.2834</td><td>0.345</td><td>0.355</td><td>0.01</td><td>11.14</td></tr><tr><td>30</td><td>39.073</td><td>13.81</td><td>22.8609</td><td>64.6810</td><td>60.4047</td><td>7.5269</td><td>12.4608</td><td>0.0862</td><td>0.3968</td><td>0.483</td><td>0.521</td><td>0.038</td><td>11.14</td></tr><tr><td>31</td><td>39.464</td><td>13.81</td><td>22.6822</td><td>64.8176</td><td>60.8807</td><td>7.6118</td><td>12.5029</td><td>0.0850</td><td>0.3910</td><td>0.476</td><td>0.527</td><td>0.051</td><td>11.14</td></tr><tr><td>32</td><td>39.789</td><td>13.81</td><td>22.5360</td><td>64.9293</td><td>61.2757</td><td>7.6824</td><td>12.5374</td><td>0.0705</td><td>0.3245</td><td>0.395</td><td>0.406</td><td>0.011</td><td>11.14</td></tr><tr><td>33</td><td>40.154</td><td>13.81</td><td>22.3739</td><td>65.0532</td><td>61.7197</td><td>7.7616</td><td>12.5756</td><td>0.0792</td><td>0.3648</td><td>0.444</td><td>0.489</td><td>0.045</td><td>11.14</td></tr><tr><td>34</td><td>40.403</td><td>13.81</td><td>22.2642</td><td>65.1370</td><td>62.0237</td><td>7.8159</td><td>12.6014</td><td>0.0543</td><td>0.2497</td><td>0.304</td><td>0.328</td><td>0.024</td><td>11.14</td></tr><tr><td>35</td><td>40.715</td><td>13.81</td><td>22.1290</td><td>65.2403</td><td>62.4027</td><td>7.8835</td><td>12.6333</td><td>0.0676</td><td>0.3114</td><td>0.379</td><td>0.394</td><td>0.015</td><td>11.14</td></tr><tr><td><b>36</b></td><td><b>40.964</b></td><td><b>13.81</b></td><td><b>22.0217</b></td><td><b>65.3223</b></td><td><b>62.7067</b></td><td><b>7.9378</b></td><td><b>12.6586</b></td><td><b>0.0543</b></td><td><b>0.2497</b></td><td><b>0.304</b></td><td><b>0.316</b></td><td><b>0.012</b></td><td><b>11.14</b></td></tr><tr><td>37</td><td>41.429</td><td>13.81</td><td>21.8251</td><td>65.4725</td><td>63.2717</td><td>8.0386</td><td>12.7049</td><td>0.1008</td><td>0.4642</td><td>0.565</td><td>0.586</td><td>0.021</td><td>12.7</td></tr><tr><td>38</td><td>41.84</td><td>13.81</td><td>21.6536</td><td>65.6036</td><td>63.7727</td><td>8.1280</td><td>12.7453</td><td>0.0894</td><td>0.4116</td><td>0.501</td><td>0.63</td><td>0.129</td><td>12.7</td></tr><tr><td>39</td><td>42.31</td><td>13.81</td><td>21.4611</td><td>65.7507</td><td>64.3447</td><td>8.2301</td><td>12.7907</td><td>0.1021</td><td>0.4699</td><td>0.572</td><td>0.611</td><td>0.039</td><td>12.7</td></tr><tr><td>40</td><td>42.606</td><td>13.81</td><td>21.3417</td><td>65.8419</td><td>64.7047</td><td>8.2944</td><td>12.8188</td><td>0.0643</td><td>0.2957</td><td>0.36</td><td>0.393</td><td>0.033</td><td>12.7</td></tr><tr><td>41</td><td>43.015</td><td>13.81</td><td>21.1787</td><td>65.9665</td><td>65.2027</td><td>8.3833</td><td>12.8572</td><td>0.0889</td><td>0.4091</td><td>0.498</td><td>0.532</td><td>0.034</td><td>12.7</td></tr><tr><td>42</td><td>43.289</td><td>13.81</td><td>21.0708</td><td>66.0489</td><td>65.5367</td><td>8.4429</td><td>12.8827</td><td>0.0596</td><td>0.2744</td><td>0.334</td><td>0.355</td><td>0.021</td><td>12.7</td></tr><tr><td>43</td><td>43.69</td><td>13.81</td><td>20.9150</td><td>66.1679</td><td>66.0247</td><td>8.5300</td><td>12.9194</td><td>0.0871</td><td>0.4009</td><td>0.488</td><td>0.556</td><td>0.068</td><td>12.7</td></tr><tr><td>44</td><td>43.928</td><td>13.81</td><td>20.8236</td><td>66.2378</td><td>66.3147</td><td>8.5817</td><td>12.9409</td><td>0.0518</td><td>0.2382</td><td>0.29</td><td>0.311</td><td>0.021</td><td>12.7</td></tr><tr><td><b>45</b></td><td><b>44.248</b></td><td><b>13.81</b></td><td><b>20.7021</b></td><td><b>66.3306</b></td><td><b>66.7037</b></td><td><b>8.6512</b></td><td><b>12.9696</b></td><td><b>0.0694</b></td><td><b>0.3196</b></td><td><b>0.389</b></td><td><b>0.441</b></td><td><b>0.052</b></td><td><b>12.7</b></td></tr><tr><td>46</td><td>44.743</td><td>13.81</td><td>20.5167</td><td>66.4724</td><td>67.3067</td><td>8.7588</td><td>13.0133</td><td>0.1076</td><td>0.4954</td><td>0.603</td><td>0.635</td><td>0.032</td><td>14.7</td></tr><tr><td>47</td><td>45.123</td><td>13.81</td><td>20.3768</td><td>66.5792</td><td>67.7687</td><td>8.8413</td><td>13.0462</td><td>0.0825</td><td>0.3795</td><td>0.462</td><td>0.507</td><td>0.045</td><td>14.7</td></tr><tr><td>48</td><td>45.633</td><td>13.81</td><td>20.1918</td><td>66.7206</td><td>68.3897</td><td>8.9521</td><td>13.0898</td><td>0.1108</td><td>0.5102</td><td>0.621</td><td>0.656</td><td>0.035</td><td>14.7</td></tr><tr><td>49</td><td>46.162</td><td>13.81</td><td>20.0034</td><td>66.8646</td><td>69.0337</td><td>9.0670</td><td>13.1342</td><td>0.1149</td><td>0.5291</td><td>0.644</td><td>0.677</td><td>0.033</td><td>14.7</td></tr><tr><td>50</td><td>46.542</td><td>13.81</td><td>19.8704</td><td>66.9662</td><td>69.4957</td><td>9.1495</td><td>13.1656</td><td>0.0825</td><td>0.3795</td><td>0.462</td><td>0.483</td><td>0.021</td><td>14.7</td></tr><tr><td><b>51</b></td><td><b>46.776</b></td><td><b>13.81</b></td><td><b>19.7893</b></td><td><b>67.0282</b></td><td><b>69.7807</b></td><td><b>9.2004</b></td><td><b>13.1847</b></td><td><b>0.0509</b></td><td><b>0.2341</b></td><td><b>0.285</b></td><td><b>0.313</b></td><td><b>0.028</b></td><td><b>14.7</b></td></tr><tr><td>52</td><td>47.483</td><td>13.81</td><td>19.5481</td><td>67.2125</td><td>70.6417</td><td>9.3541</td><td>13.2415</td><td>0.1537</td><td>0.7073</td><td>0.861</td><td>0.883</td><td>0.022</td><td>17.5</td></tr><tr><td>53</td><td>48.067</td><td>13.81</td><td>19.3533</td><td>67.3614</td><td>71.3527</td><td>9.4810</td><td>13.2875</td><td>0.1269</td><td>0.5841</td><td>0.711</td><td>0.739</td><td>0.028</td><td>17.5</td></tr><tr><td>54</td><td>48.48</td><td>13.81</td><td>19.2181</td><td>67.4647</td><td>71.8547</td><td>9.5706</td><td>13.3193</td><td>0.0896</td><td>0.4124</td><td>0.502</td><td>0.54</td><td>0.038</td><td>17.5</td></tr><tr><td>55</td><td>49.338</td><td>13.81</td><td>18.9426</td><td>67.6752</td><td>72.8997</td><td>9.7571</td><td>13.3842</td><td>0.1865</td><td>0.8585</td><td>1.045</td><td>1.372</td><td>0.327</td><td>17.5</td></tr><tr><td>56</td><td>49.617</td><td>13.81</td><td>18.8549</td><td>67.7422</td><td>73.2387</td><td>9.8176</td><td>13.4049</td><td>0.0605</td><td>0.2785</td><td>0.339</td><td>0.359</td><td>0.02</td><td>17.5</td></tr><tr><td>57</td><td>50.161</td><td>13.81</td><td>18.6857</td><td>67.8715</td><td>73.9017</td><td>9.9359</td><td>13.4448</td><td>0.1183</td><td>0.5447</td><td>0.663</td><td>0.69</td><td>0.027</td><td>17.5</td></tr><tr><td>58</td><td>50.67</td><td>13.81</td><td>18.5305</td><td>67.9901</td><td>74.5207</td><td>10.0464</td><td>13.4814</td><td>0.1105</td><td>0.5085</td><td>0.619</td><td>0.645</td><td>0.026</td><td>17.5</td></tr><tr><td>59</td><td>51.158</td><td>13.81</td><td>18.3840</td><td>68.1021</td><td>75.1147</td><td>10.1524</td><td>13.5159</td><td>0.1060</td><td>0.4880</td><td>0.594</td><td>0.606</td><td>0.012</td><td>17.5</td></tr><tr><td>60</td><td>51.917</td><td>13.81</td><td>18.1606</td><td>68.2728</td><td>76.0387</td><td>10.3173</td><td>13.5685</td><td>0.1649</td><td>0.7591</td><td>0.924</td><td>0.942</td><td>0.018</td><td>17.5</td></tr><tr><td>61</td><td>52.75</td><td>13.81</td><td>17.9216</td><td>68.4554</td><td>77.0527</td><td>10.4983</td><td>13.6249</td><td>0.1810</td><td>0.8330</td><td>1.014</td><td>1.114</td><td>0.1</td><td>17.5</td></tr><tr><td><b>62</b></td><td><b>53.161</b></td><td><b>13.81</b></td><td><b>17.8058</b></td><td><b>68.5439</b></td><td><b>77.5537</b></td><td><b>10.5877</b></td><td><b>13.6522</b></td><td><b>0.0894</b></td><td><b>0.4116</b></td><td><b>0.501</b></td><td><b>0.532</b></td><td><b>0.031</b></td><td><b>17.5</b></td></tr><tr><td>63</td><td>53.62</td><td>13.81</td><td>17.6786</td><td>68.6411</td><td>78.1111</td><td>10.6873</td><td>13.6821</td><td>0.0996</td><td>0.4584</td><td>0.558</td><td>0.571</td><td>0.013</td><td>19.63</td></tr><tr><td>64</td><td>54.143</td><td>13.81</td><td>17.5356</td><td>68.7503</td><td>78.7487</td><td>10.8010</td><td>13.7158</td><td>0.1137</td><td>0.5233</td><td>0.637</td><td>0.654</td><td>0.017</td><td>19.65</td></tr><tr><td>65</td><td>54.749</td><td>13.81</td><td>17.3730</td><td>68.8746</td><td>79.4857</td><td>10.9326</td><td>13.7542</td><td>0.1315</td><td>0.6055</td><td>0.737</td><td>0.755</td><td>0.018</td><td>19.65</td></tr><tr><td>66</td><td>55.331</td><td>13.81</td><td>17.2194</td><td>68.9920</td><td>80.1947</td><td>11.0591</td><td>13.7904</td><td>0.1265</td><td>0.5825</td><td>0.709</td><td>0.736</td><td>0.027</td><td>19.65</td></tr><tr><td>67</td><td>55.919</td><td>13.81</td><td>17.0671</td><td>69.1084</td><td>80.9107</td><td>11.1869</td><td>13.8263</td><td>0.1278</td><td>0.5882</td><td>0.716</td><td>0.745</td><td>0.029</td><td>19.65</td></tr><tr><td>68</td><td>56.857</td><td>13.81</td><td>16.8295</td><td>69.2899</td><td>82.0527</td><td>11.3908</td><td>13.8822</td><td>0.2038</td><td>0.9382</td><td>1.142</td><td>1.198</td><td>0.056</td><td>19.65</td></tr><tr><td>69</td><td>57.446</td><td>13.81</td><td>16.6839</td><td>69.4012</td><td>82.7687</td><td>11.5186</td><td>13.9166</td><td>0.1278</td><td>0.5882</td><td>0.716</td><td>0.743</td><td>0.027</td><td>19.65</td></tr><tr><td>70</td><td>57.851</td><td>13.81</td><td>16.5850</td><td>69.4768</td><td>83.2627</td><td>11.6067</td><td>13.9399</td><td>0.0882</td><td>0.4058</td><td>0.494</td><td>0.517</td><td>0.023</td><td>19.65</td></tr><tr><td>71</td><td>58.164</td><td>13.81</td><td>16.5094</td><td>69.5346</td><td>83.6437</td><td>11.6747</td><td>13.9577</td><td>0.0680</td><td>0.3130</td><td>0.381</td><td>0.408</td><td>0.027</td><td>19.65</td></tr><tr><td>72</td><td>58.45</td><td>13.81</td><td>16.4412</td><td>69.5867</td><td>83.9907</td><td>11.7367</td><td>13.9738</td><td>0.0619</td><td>0.2851</td><td>0.347</td><td>0.362</td><td>0.015</td><td>19.65</td></tr><tr><td>73</td><td>59.021</td><td>13.81</td><td>16.3061</td><td>69.6899</td><td>84.6867</td><td>11.8609</td><td>14.0056</td><td>0.1242</td><td>0.5718</td><td>0.696</td><td>0.739</td><td>0.043</td><td>19.65</td></tr><tr><td>74</td><td>59.567</td><td>13.81</td><td>16.1792</td><td>69.7869</td><td>85.3507</td><td>11.9794</td><td>14.0355</td><td>0.1185</td><td>0.5455</td><td>0.664</td><td>0.684</td><td>0.02</td><td>19.65</td></tr><tr><td>75</td><td>59.863</td><td>13.81</td><td>16.1113</td><td>69.8388</td><td>85.7107</td><td>12.0437</td><td>14.0515</td><td>0.0643</td><td>0.2957</td><td>0.36</td><td>0.386</td><td>0.026</td><td>19.65</td></tr><tr><td>76</td><td>60.171</td><td>13.81</td><td>16.0411</td><td>69.8924</td><td>86.0857</td><td>12.1106</td><td>14.0681</td><td>0.0669</td><td>0.3081</td><td>0.375</td><td>0.393</td><td>0.018</td><td>19.65</td></tr><tr><td>77</td><td>60.452</td><td>13.81</td><td>15.9776</td><td>69.9410</td><td>86.4277</td><td>12.1716</td><td>14.0830</td><td>0.0610</td><td>0.2810</td><td>0.342</td><td>0.362</td><td>0.02</td><td>19.65</td></tr><tr><td><b>78</b></td><td><b>60.842</b></td><td><b>13.81</b></td><td><b>15.8903</b></td><td><b>70.0077</b></td><td><b>86.9027</b></td><td><b>12.2564</b></td><td><b>14.1036</b></td><td><b>0.0848</b></td><td><b>0.3902</b></td><td><b>0.475</b></td><td><b>0.495</b></td><td><b>0.02</b></td><td><b>19.65</b></td></tr></tbody></table>

IL = [BMIM]FeCl₄.

Bold markings are used to indicate saturation points.
<table><caption>**Table B7**
Absolute and relative uncertainties for atmospheric reactor experiment 3.</caption><caption>[BMIM]FeCl<sub>4</sub> + H<sub>2</sub>O + 12–14 wt% NaCl</caption><thead><tr><th colspan="11">Experiment 3</th></tr><tr><th rowspan="2">Number</th><th colspan="10">ΔInside the vessel ±</th><th rowspan="2">NaCl, g</th><th rowspan="2">H<sub>2</sub>O, g</th><th rowspan="2">Solution, g</th><th rowspan="2">Weighed, g</th><th rowspan="2">Left, g</th><th rowspan="2">Temp, C</th></tr><tr><th>H<sub>2</sub>O, g</th><th>IL, g</th><th>IL, wt%</th><th>H<sub>2</sub>O, wt%</th><th>Solution, g</th><th>NaCl, g</th><th>NaCl, wt%</th></tr></thead><tbody><tr><td>0</td><td>0.0141</td><td>0.014</td><td>0.0973</td><td>0.0798</td><td>0.0141</td><td>0.0000</td><td>0.0000</td><td>0.0000</td><td></td><td></td><td></td><td></td><td></td><td>7.47</td></tr><tr><td>1</td><td>0.0202</td><td>0.014</td><td>0.0427</td><td>0.0612</td><td>0.0200</td><td>0.0026</td><td>0.0084</td><td>0.0026</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>7.63</td></tr><tr><td>2</td><td>0.0248</td><td>0.014</td><td>0.0410</td><td>0.0704</td><td>0.0245</td><td>0.0036</td><td>0.0107</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>7.5</td></tr><tr><td>3</td><td>0.0286</td><td>0.014</td><td>0.0413</td><td>0.0795</td><td>0.0283</td><td>0.0044</td><td>0.0127</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>7.6</td></tr><tr><td>4</td><td>0.032</td><td>0.014</td><td>0.0400</td><td>0.0850</td><td>0.0316</td><td>0.0051</td><td>0.0139</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>7.58</td></tr><tr><td>5</td><td>0.0351</td><td>0.014</td><td>0.0383</td><td>0.0885</td><td>0.0346</td><td>0.0057</td><td>0.0148</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>7.6</td></tr><tr><td>6</td><td>0.0379</td><td>0.014</td><td>0.0382</td><td>0.0939</td><td>0.0374</td><td>0.0062</td><td>0.0158</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>7.6</td></tr><tr><td>7</td><td>0.0406</td><td>0.014</td><td>0.0370</td><td>0.0967</td><td>0.0400</td><td>0.0067</td><td>0.0165</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>7.61</td></tr><tr><td>8</td><td>0.043</td><td>0.014</td><td>0.0354</td><td>0.0980</td><td>0.0424</td><td>0.0072</td><td>0.0169</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>7.6</td></tr><tr><td>9</td><td>0.0454</td><td>0.014</td><td>0.0356</td><td>0.1023</td><td>0.0447</td><td>0.0076</td><td>0.0177</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>7.6</td></tr><tr><td>10</td><td>0.0476</td><td>0.014</td><td>0.0358</td><td>0.1063</td><td>0.0469</td><td>0.0080</td><td>0.0184</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>7.6</td></tr><tr><td>11</td><td>0.0497</td><td>0.014</td><td>0.0359</td><td>0.1099</td><td>0.0490</td><td>0.0084</td><td>0.0191</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>7.6</td></tr><tr><td>12</td><td>0.0517</td><td>0.014</td><td>0.0360</td><td>0.1134</td><td>0.0510</td><td>0.0088</td><td>0.0198</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>7.33</td></tr><tr><td>13</td><td>0.0537</td><td>0.014</td><td>0.0361</td><td>0.1165</td><td>0.0529</td><td>0.0091</td><td>0.0204</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>7.38</td></tr><tr><td>14</td><td>0.0556</td><td>0.014</td><td>0.0363</td><td>0.1198</td><td>0.0548</td><td>0.0095</td><td>0.0210</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>7.47</td></tr><tr><td>15</td><td>0.0574</td><td>0.014</td><td>0.0364</td><td>0.1227</td><td>0.0566</td><td>0.0098</td><td>0.0216</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>7.47</td></tr><tr><td>16</td><td>0.0592</td><td>0.014</td><td>0.0365</td><td>0.1255</td><td>0.0583</td><td>0.0101</td><td>0.0221</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>7.5</td></tr><tr><td><b>17</b></td><td><b>0.0609</b></td><td><b>0.014</b></td><td><b>0.0367</b></td><td><b>0.1285</b></td><td><b>0.0600</b></td><td><b>0.0104</b></td><td><b>0.0227</b></td><td><b>0.0025</b></td><td><b>0.0144</b></td><td><b>0.0141</b></td><td><b>0.01</b></td><td><b>0.01</b></td><td><b>7.5</b></td></tr><tr><td>18</td><td>0.0626</td><td>0.014</td><td>0.0369</td><td>0.1313</td><td>0.0616</td><td>0.0107</td><td>0.0232</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>9.3</td></tr><tr><td>19</td><td>0.0642</td><td>0.014</td><td>0.0371</td><td>0.1340</td><td>0.0632</td><td>0.0110</td><td>0.0237</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>9.3</td></tr><tr><td>20</td><td>0.0658</td><td>0.014</td><td>0.0373</td><td>0.1368</td><td>0.0648</td><td>0.0113</td><td>0.0242</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>9.3</td></tr><tr><td>21</td><td>0.0673</td><td>0.014</td><td>0.0376</td><td>0.1394</td><td>0.0663</td><td>0.0116</td><td>0.0247</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>9.29</td></tr><tr><td>22</td><td>0.0689</td><td>0.014</td><td>0.0378</td><td>0.1420</td><td>0.0678</td><td>0.0118</td><td>0.0252</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>9.29</td></tr><tr><td>23</td><td>0.0703</td><td>0.014</td><td>0.0380</td><td>0.1445</td><td>0.0693</td><td>0.0121</td><td>0.0257</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>9.3</td></tr><tr><td><b>24</b></td><td><b>0.0718</b></td><td><b>0.014</b></td><td><b>0.0382</b></td><td><b>0.1469</b></td><td><b>0.0707</b></td><td><b>0.0124</b></td><td><b>0.0261</b></td><td><b>0.0025</b></td><td><b>0.0144</b></td><td><b>0.0141</b></td><td><b>0.01</b></td><td><b>0.01</b></td><td><b>9.3</b></td></tr><tr><td>25</td><td>0.0732</td><td>0.014</td><td>0.0380</td><td>0.1485</td><td>0.0721</td><td>0.0126</td><td>0.0264</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>11.2</td></tr><tr><td>26</td><td>0.0746</td><td>0.014</td><td>0.0379</td><td>0.1501</td><td>0.0735</td><td>0.0129</td><td>0.0268</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>11.14</td></tr><tr><td>27</td><td>0.076</td><td>0.014</td><td>0.0380</td><td>0.1520</td><td>0.0748</td><td>0.0131</td><td>0.0271</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>11.14</td></tr><tr><td>28</td><td>0.0773</td><td>0.014</td><td>0.0380</td><td>0.1537</td><td>0.0762</td><td>0.0134</td><td>0.0275</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>11.14</td></tr><tr><td>29</td><td>0.0786</td><td>0.014</td><td>0.0380</td><td>0.1555</td><td>0.0775</td><td>0.0136</td><td>0.0278</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>11.14</td></tr><tr><td>30</td><td>0.0799</td><td>0.014</td><td>0.0379</td><td>0.1569</td><td>0.0787</td><td>0.0138</td><td>0.0281</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>11.14</td></tr><tr><td>31</td><td>0.0812</td><td>0.014</td><td>0.0378</td><td>0.1583</td><td>0.0800</td><td>0.0141</td><td>0.0283</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>11.14</td></tr><tr><td>32</td><td>0.0825</td><td>0.014</td><td>0.0378</td><td>0.1598</td><td>0.0812</td><td>0.0143</td><td>0.0286</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>11.14</td></tr><tr><td>33</td><td>0.0837</td><td>0.014</td><td>0.0377</td><td>0.1611</td><td>0.0825</td><td>0.0145</td><td>0.0289</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>11.14</td></tr><tr><td>34</td><td>0.085</td><td>0.014</td><td>0.0377</td><td>0.1627</td><td>0.0837</td><td>0.0147</td><td>0.0292</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>11.14</td></tr><tr><td>35</td><td>0.0862</td><td>0.014</td><td>0.0377</td><td>0.1641</td><td>0.0849</td><td>0.0149</td><td>0.0295</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>11.14</td></tr><tr><td><b>36</b></td><td><b>0.0873</b></td><td><b>0.014</b></td><td><b>0.0377</b></td><td><b>0.1656</b></td><td><b>0.0860</b></td><td><b>0.0152</b></td><td><b>0.0298</b></td><td><b>0.0025</b></td><td><b>0.0144</b></td><td><b>0.0141</b></td><td><b>0.01</b></td><td><b>0.01</b></td><td><b>11.14</b></td></tr><tr><td>37</td><td>0.0885</td><td>0.014</td><td>0.0375</td><td>0.1665</td><td>0.0872</td><td>0.0154</td><td>0.0299</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>12.7</td></tr><tr><td>38</td><td>0.0897</td><td>0.014</td><td>0.0373</td><td>0.1674</td><td>0.0883</td><td>0.0156</td><td>0.0301</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>12.7</td></tr><tr><td>39</td><td>0.0908</td><td>0.014</td><td>0.0371</td><td>0.1681</td><td>0.0894</td><td>0.0158</td><td>0.0303</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>12.7</td></tr><tr><td>40</td><td>0.092</td><td>0.014</td><td>0.0370</td><td>0.1694</td><td>0.0906</td><td>0.0160</td><td>0.0305</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>12.7</td></tr><tr><td>41</td><td>0.0931</td><td>0.014</td><td>0.0368</td><td>0.1702</td><td>0.0917</td><td>0.0162</td><td>0.0307</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>12.7</td></tr><tr><td>42</td><td>0.0942</td><td>0.014</td><td>0.0368</td><td>0.1714</td><td>0.0927</td><td>0.0164</td><td>0.0309</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>12.7</td></tr><tr><td>43</td><td>0.0953</td><td>0.014</td><td>0.0366</td><td>0.1722</td><td>0.0938</td><td>0.0166</td><td>0.0311</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>12.7</td></tr><tr><td>44</td><td>0.0963</td><td>0.014</td><td>0.0366</td><td>0.1734</td><td>0.0949</td><td>0.0167</td><td>0.0313</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>12.7</td></tr><tr><td><b>45</b></td><td><b>0.0974</b></td><td><b>0.014</b></td><td><b>0.0365</b></td><td><b>0.1744</b></td><td><b>0.0959</b></td><td><b>0.0169</b></td><td><b>0.0315</b></td><td><b>0.0025</b></td><td><b>0.0144</b></td><td><b>0.0141</b></td><td><b>0.01</b></td><td><b>0.01</b></td><td><b>12.7</b></td></tr><tr><td>46</td><td>0.0985</td><td>0.014</td><td>0.0363</td><td>0.1748</td><td>0.0970</td><td>0.0171</td><td>0.0316</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>14.7</td></tr><tr><td>47</td><td>0.0995</td><td>0.014</td><td>0.0361</td><td>0.1756</td><td>0.0980</td><td>0.0173</td><td>0.0318</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>14.7</td></tr><tr><td>48</td><td>0.1005</td><td>0.014</td><td>0.0358</td><td>0.1759</td><td>0.0990</td><td>0.0175</td><td>0.0318</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>14.7</td></tr><tr><td>49</td><td>0.1015</td><td>0.014</td><td>0.0355</td><td>0.1761</td><td>0.1000</td><td>0.0177</td><td>0.0319</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>14.7</td></tr><tr><td>50</td><td>0.1026</td><td>0.014</td><td>0.0353</td><td>0.1768</td><td>0.1010</td><td>0.0179</td><td>0.0320</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>14.7</td></tr><tr><td><b>51</b></td><td><b>0.1036</b></td><td><b>0.014</b></td><td><b>0.0353</b></td><td><b>0.1778</b></td><td><b>0.1020</b></td><td><b>0.0180</b></td><td><b>0.0322</b></td><td><b>0.0025</b></td><td><b>0.0144</b></td><td><b>0.0141</b></td><td><b>0.01</b></td><td><b>0.01</b></td><td><b>14.7</b></td></tr><tr><td>52</td><td>0.1046</td><td>0.014</td><td>0.0348</td><td>0.1775</td><td>0.1030</td><td>0.0182</td><td>0.0322</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>17.5</td></tr><tr><td>53</td><td>0.1055</td><td>0.014</td><td>0.0345</td><td>0.1775</td><td>0.1039</td><td>0.0184</td><td>0.0322</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>17.5</td></tr><tr><td>54</td><td>0.1065</td><td>0.014</td><td>0.0343</td><td>0.1779</td><td>0.1049</td><td>0.0186</td><td>0.0323</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>17.5</td></tr><tr><td>55</td><td>0.1075</td><td>0.014</td><td>0.0337</td><td>0.1772</td><td>0.1058</td><td>0.0187</td><td>0.0322</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>17.5</td></tr><tr><td>56</td><td>0.1084</td><td>0.014</td><td>0.0336</td><td>0.1780</td><td>0.1068</td><td>0.0189</td><td>0.0324</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>17.5</td></tr><tr><td>57</td><td>0.1094</td><td>0.014</td><td>0.0333</td><td>0.1780</td><td>0.1077</td><td>0.0191</td><td>0.0324</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>17.5</td></tr><tr><td>58</td><td>0.1103</td><td>0.014</td><td>0.0330</td><td>0.1781</td><td>0.1086</td><td>0.0192</td><td>0.0324</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>17.5</td></tr><tr><td>59</td><td>0.1112</td><td>0.014</td><td>0.0328</td><td>0.1783</td><td>0.1095</td><td>0.0194</td><td>0.0325</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>17.5</td></tr><tr><td>60</td><td>0.1122</td><td>0.014</td><td>0.0323</td><td>0.1777</td><td>0.1105</td><td>0.0196</td><td>0.0324</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>17.5</td></tr><tr><td>61</td><td>0.1131</td><td>0.014</td><td>0.0317</td><td>0.1770</td><td>0.1114</td><td>0.0197</td><td>0.0323</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>17.5</td></tr><tr><td><b>62</b></td><td><b>0.114</b></td><td><b>0.014</b></td><td><b>0.0316</b></td><td><b>0.1773</b></td><td><b>0.1122</b></td><td><b>0.0199</b></td><td><b>0.0324</b></td><td><b>0.0025</b></td><td><b>0.0144</b></td><td><b>0.0141</b></td><td><b>0.01</b></td><td><b>0.01</b></td><td><b>17.5</b></td></tr><tr><td>63</td><td>0.1149</td><td>0.014</td><td>0.0314</td><td>0.1775</td><td>0.1131</td><td>0.0200</td><td>0.0324</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>19.63</td></tr><tr><td>64</td><td>0.1158</td><td>0.014</td><td>0.0311</td><td>0.1776</td><td>0.1140</td><td>0.0202</td><td>0.0324</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>19.65</td></tr><tr><td>65</td><td>0.1167</td><td>0.014</td><td>0.0308</td><td>0.1774</td><td>0.1149</td><td>0.0204</td><td>0.0324</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>19.65</td></tr><tr><td>66</td><td>0.1176</td><td>0.014</td><td>0.0305</td><td>0.1772</td><td>0.1158</td><td>0.0205</td><td>0.0324</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>19.65</td></tr><tr><td>67</td><td>0.1184</td><td>0.014</td><td>0.0302</td><td>0.1770</td><td>0.1166</td><td>0.0207</td><td>0.0324</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>19.65</td></tr><tr><td>68</td><td>0.1193</td><td>0.014</td><td>0.0296</td><td>0.1760</td><td>0.1175</td><td>0.0208</td><td>0.0322</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>19.65</td></tr><tr><td>69</td><td>0.1202</td><td>0.014</td><td>0.0293</td><td>0.1758</td><td>0.1183</td><td>0.0210</td><td>0.0322</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>19.65</td></tr><tr><td>70</td><td>0.121</td><td>0.014</td><td>0.0292</td><td>0.1761</td><td>0.1192</td><td>0.0211</td><td>0.0323</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>19.65</td></tr></tbody></table>

(continued on next page)
<table><caption>Table B7 (continued)</caption><caption>[BMIM][FeCl<sub>4</sub> + H<sub>2</sub>O + 12–14 wt% NaCl]</caption><thead><tr><th colspan="10">Experiment 3</th></tr><tr><th colspan="10">ΔInside the vessel ±</th></tr><tr><th>Number</th><th>H<sub>2</sub>O, g</th><th>IL, g</th><th>IL, wt%</th><th>H<sub>2</sub>O, wt%</th><th>Solution, g</th><th>NaCl, g</th><th>NaCl, wt%</th><th>NaCl, g</th><th>H<sub>2</sub>O, g</th><th>Solution, g</th><th>Weighed, g</th><th>Left, g</th><th>Temp, C</th></tr></thead><tbody><tr><td>71</td><td>0.1219</td><td>0.014</td><td>0.0291</td><td>0.1766</td><td>0.1200</td><td>0.0213</td><td>0.0324</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>19.65</td></tr><tr><td>72</td><td>0.1227</td><td>0.014</td><td>0.0290</td><td>0.1771</td><td>0.1208</td><td>0.0214</td><td>0.0325</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>19.65</td></tr><tr><td>73</td><td>0.1236</td><td>0.014</td><td>0.0288</td><td>0.1769</td><td>0.1217</td><td>0.0216</td><td>0.0325</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>19.65</td></tr><tr><td>74</td><td>0.1244</td><td>0.014</td><td>0.0285</td><td>0.1768</td><td>0.1225</td><td>0.0217</td><td>0.0325</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>19.65</td></tr><tr><td>75</td><td>0.1252</td><td>0.014</td><td>0.0284</td><td>0.1773</td><td>0.1233</td><td>0.0219</td><td>0.0325</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>19.65</td></tr><tr><td>76</td><td>0.126</td><td>0.014</td><td>0.0284</td><td>0.1777</td><td>0.1241</td><td>0.0220</td><td>0.0326</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>19.65</td></tr><tr><td>77</td><td>0.1268</td><td>0.014</td><td>0.0283</td><td>0.1782</td><td>0.1249</td><td>0.0222</td><td>0.0327</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>19.65</td></tr><tr><td>78</td><td>0.1277</td><td>0.014</td><td>0.0282</td><td>0.1784</td><td>0.1257</td><td>0.0223</td><td>0.0328</td><td>0.0025</td><td>0.0144</td><td>0.0141</td><td>0.01</td><td>0.01</td><td>19.65</td></tr></tbody></table>

$$IL = [\text{BMIM}]\text{FeCl}_4$$

Bold markings are used to indicate saturation points.

## Data availability

Data will be made available on request.

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