Isobutyric Acid Water Research Articles

Liquid–Liquid Demonstrations: Critical Opalescence

In the vicinity of a critical point, the impact of a substance’s chemical identity is superseded by universal critical behavior for a number of physical properties, such as visible light scattering. In this classroom demonstration, students observe a single-phase critical mixture of partially miscible isobutyric acid + water (IAW) as the liquid–liquid sample cools down to its critical temperature. Students see the sample change from colorless and transparent, to pale blue, to white and turbid. This optical behavior is called critical opalescence. No pressure control is necessary for the demonstration since the system is a condensed phase, so the sample can be large (100 mL here) and suitable for classroom visualization. The experiment is easy to set up and highly repeatable because the critical temperature of the IAW system is just above room temperature. The demonstration can be used to show the difference in angular dependence for light scattering from a single-phase sample versus a two-phase sample containing a suspension of droplets, and also to segue to a conversation on why the sky is blue. Furthermore, the critical IAW sample may be incorporated into a quantitative classroom demonstration or laboratory project in which laser light scattering measured at 90° of incidence is used to calculate the correlation length amplitude ξ0 of the IAW system and the universal critical exponent ν.

Gel Volume Near the Critical Point of Binary Mixture Isobutyric Acid-Water.

The volume of a cylindrical polyacrylamide gel was measured when immersed in a binary mixture of isobutyric acid–water at different temperatures and weight fractions of isobutyric acid. Near the upper critical solution temperature of the binary mixture, the curve for gel volume vs. isobutyric acid weight fraction has a shoulder or a peak near the critical weight fraction. On the other hand, in a region away from the critical temperature, the gel volume decreased monotonically with increasing isobutyric acid weight fraction. The cloud point temperature of the binary mixture inside the gel was lower than that outside the gel. Thermodynamic description for the gel in the critical mixture is derived on the basis of the Ising model. By the description, the experimental results are explained consistently. The theoretical analysis shows that the shoulder and the peak appearing in the swelling behavior of the gel are respectively induced by the criticalities of the binary mixture outside and inside the gel. It also shows that the cloud point temperature lowering of the binary mixture inside the gel is attributed to the effective enhancement of the temperature of the binary mixture inside the gel induced by the presence of the gel polymer.

Compensating effect of ultrasonic waves on retarding action of nanoparticles in drops liquid–liquid extraction

The influence of ultrasonic waves on liquid–liquid extraction of circulating drops and in the presence of magnetite nanoparticles was investigated. Experiments were conducted in a column equipped with an ultrasound transducer. The frequency and intensity of received waves, measured by the hydrophone standard method, were 35.40 kHz and 0.37 mW/cm2, respectively. The recommended chemical system of cumene–isobutyric acid–water was used in which mass transfer resistance lies in the aqueous phase. Nanoparticles, within concentration range of (0.0003–0.0030) wt%, were added to the aqueous continuous phase. The presence of nanoparticles and ultrasonic waves provided no sensible change in drop size (within 2.49–4.17 mm) and measured terminal velocities were close to Grace model. However, presence of nanoparticles, caused mass transfer to decrease. This undesired effect was significantly diminished by using ultrasonic waves so that mass transfer coefficient increased from (73.0–178.2) to (130.2–240.2) µm/s, providing a 55.6% average enhancement. It is presumably due to disturbing the accumulated nanoparticles around the drops. The current innovative study highlights the fact that using ultrasonic waves is an interesting way to improve liquid–liquid extraction in the presence and absence of nanoparticles.

Experimental studies on the effect of ultrasonic waves on single drop liquid–liquid extraction

The influence of ultrasonic waves on hydrodynamics and mass transfer of circulating drops in liquid–liquid extraction process was studied. The recommended chemical systems of toluene–acetic acid–water with mass transfer resistance mainly in the organic phase, and cumene–isobutyric acid–water in the aqueous phase were used. An extraction column, equipped with an ultrasonic emitter of 35.40kHz real frequency and 0.37mW/cm2 intensity, was employed. The ultrasound properties were measured using the hydrophone standard method. Drops terminal velocity was comparable with the Grace model. In mass transfer study, significant enhancement was revealed in overall mass transfer coefficient for different drop sizes and for the both mass transfer directions by using ultrasonic waves. The average and maximum enhancements were, respectively, 20.8 and 31.7% for toluene–acetic acid–water, and 40.3 and 55.1% for cumene–isobutyric acid–water. Small drops exhibited a higher enhancement percentage. Regarding the mass transfer direction, the system of cumene–isobutyric acid–water with continuous to dispersed phase direction, was benefited more as the consequence of creating effective agitation in continuous phase than in dispersed phase.

Temperature dependence of the viscosity of the isobutyric acid-water solution along the critical isoconcentrate and phase interface

The temperature dependences of regular and fluctuation parts of viscosity along critical isoconcentrate and phase interface have been studied on the basis of data of shear viscosity behavior of isobutyric acid-water solution near the critical consolute temperature. New method for studying the viscosity on separate branches of the coexistence curve has been proposed for the first time. The viscosity equation, which is connected with the correlation length of the system and takes into account the spatial dispersion, has been used for the experimental data analysis.

Performance improving with temperature in liquid–liquid extraction using cumene–isobutyric acid–water chemical system

The performance of single drops was investigated in liquid–liquid extraction while temperature was changed within the range of 15–40°C. The recommended system of cumene–isobutyric acid–water with mass transfer resistance mainly in aqueous phase was used. An average enhancement of 75.6% in the rate of transfer was revealed. The extraction efficiency is the most influencing term due to molecular diffusivity enhancement. For modeling, a simple correlation was proposed for the effective diffusivity in Newman's equation, while continuous phase mass transfer coefficient was directly included. Using this model, relative deviation of the overall mass transfer coefficient was within only ±5.6%.

Treatment of Herráez equation correlating viscosity in binary liquid mixtures exhibiting strictly monotonous distribution

Recently, Herráez et al. proposed a new correlation equation, which introduces a correcting polynomial as an exponential-acting upon the molar fraction of one of mixture components. This equation is found to be widely applicable with more reasonable accuracy in systems exhibiting monotonous distribution than those presenting an extremum. In previous works, we have found that the first adjustable parameter of this equation is a universal exponent (0.5 or 1) for dioxane–water and isobutyric acid–water mixtures characterising the presence of solute–solute or solute–solvent interaction at very high dilution. In this work, we have tested this equation in 48 systems, and we have noted that several data on binary mixtures exhibiting monotonous variation are well represented by the two sides of this equation. We have mathematically justified the four distinct values of the universal exponent classifying the nature of each solute–solvent couple in dilute region.

Effect of structural variations in cations of ionic liquids on the coexistence curve of isobutyric acid and water

Interestingly, various behaviors of ionic liquids (ILs) having different cation chains with a common anion is observed in the coexistence curve of isobutyric acid–water (IBW). The critical region of IBW was found to increase in the presence of aliphatic chain 1-hexyl-3-methyl-imidazolium tetrafluoroborate [C6mim][BF4], (IL-1) whereas the critical region decreased in the presence of aromatic chain 1-benzyl-3-methylimidazolium tetrafluoroborate [Bnmim][BF4], (IL-2). Adding 0.5–2.0 mg ml−1 of IL-1 or IL-2 to IBW caused the critical temperature (Tc) to decrease by 0.553–2.898 K (for IL-1) and to increase by 0.502–1.664 K (for IL-2). The critical exponent (β) increases with increasing the IL concentrations, which are fully renormalized critical exponents. Further, our dynamic light scattering (DLS) results for the binary critical solution of IBW indicate that there exists a fluctuation in the local density that contributes significantly to the fluctuations in the scattered intensity at Tc. The variations in fluctuations are found to be pronounced in the presence of IL as an impurity. The reason for this behavior may be the formation of large water clusters with the neighboring molecules of ILs at Tc. This indicates that the IL entangles with the both coexisting phases, thereby, the IL strongly interacts with the neighboring solvent molecules. In addition, we report the fluorescence spectroscopy data for the critical mixture of IBW and its mixture with ILs as impurities using Nile Red as a fluorescent probe. Noticeable transitions of the two phases were detected at Tc through fluorescence technique. The observed variations in the fluorescence intensities with temperature predict unambiguously the formation of the solvation structure at Tc for the pure critical mixture as well as in presence of ILs.

Density, viscosity and electrical conductivity of isobutyric acid–water with added ions in the critical regions

Density, viscosity and electrical conductivity of the six concentrated binary ionic mixtures of isobutyric acid–water with X M [KCl] at the critical concentrations were measured as functions of temperature (ΔT = T − T c ≤ 2 K) and at various compositions, X, in the critical regions. The molar volumes have been calculated from their densities. The molar volume data dependence of viscosity and conductivity has been fitted to an equation similar to the Vogel–Tammann–Fulcher (VTF) based on the free volume model. The concentration of ions (K+, Cl−), dependence of the Vogel temperature, the intrinsic volume and the transport properties are primarily governed by the existence of intermolecular interactions.

Excess conductivities of isobutyric acid + water binary mixtures near and far away from the critical temperature

The excess conductivities, σ E and excess energy of activation (ΔEσ )E of electrical conductivity have been investigated by using electrical conductivities measurements for isobutyric acid + water (IBAW) mixtures over the entire range of mole fractions at six different temperatures, both near and close to the critical temperature (0.055 < (T–T c)/K < 13.055). The results were also fitted with the Redlich–Kister equation. This system exhibited very large negative values of σE and very large positive values of (ΔEσ )E due to increased hydrogen bonding interactions and correlation length between unlike molecules in the critical region, and to very large differences between the molar volumes of the pure components at low temperatures. The activation parameters ΔHσ and ΔSσ have also been calculated, and show that the critical region has an important effect on the electrical conductivity properties.

Excess permittivity and excess conductivity of binary fluid mixture isobutyric acid – water along the coexistence curve

Excess permittivity and excess conductivity of the binary fluid mixture isobutyric acid–water (I–W) have been computed at three temperatures and along the coexistence curve, on the basis of refractive index and electrical conductivity data of the mixture. The other related properties, molar volume, molar refraction and polarisablities have also been reported. The temperature dependence of the molar refraction was also examined. The results have been interpreted in terms of the nature of specific intermolecular interactions between the components.

Studying diffusion of partially miscible and systems near their consolute point by laser line deflection

We propose that miscible systems can be divided into three types: miscible in all proportions, partially miscible but not near a consulate point, and a system with a consulate point. We studied two types of miscible systems by laser line deflection (LLD) in order to understand behavior observed in a spinning drop tensiometer; namely, that some miscible drops became diffuse over time while others maintained a sharp concentration profile as the drop dissolved. We previously studied a miscible system, dodecyl acrylate–poly(dodecyl acrylate) using LLD and found that the system relaxed as expected with a concentration-independent diffusion coefficient. We used LLD to study two other miscible systems: 1-butanol–water, and isobutyric acid–water above the latter's upper critical solution temperature (UCST). The transition zone boundaries in the 1-butanol and water system propagated into the component that was not saturated with the other component. The boundaries propagated with a t 0.09. When an equilibrated IBA–water system was heated above its UCST (26 °C), the transition zone propagated into the IBA-rich region. The propagation exhibited t 0.06 behavior. The propagation of transition zone boundaries showed the same qualitative behavior under 1 g acceleration in the LLD experiments as under the higher acceleration in the tensiometer so it is not necessary to invoke barodiffusion as the cause of the behavior although it may still affect the rate of diffusion.

Electrical conductivity of the binary mixture isobutyric acid–water with added (Zn 2+, SO 42−) ions

Precise electrical conductivity σ (mS cm −1) measurements for isobutyric acid–water mixtures with added Zn 2+ and SO 4 2− ions have been performed in the Arrhenius temperature domain of the studied electrolyte and for different fractional composition of IBA in the range from 16 mass% to 80 mass%. The temperature dependence of the electrical conductivity of the studied mixtures obeys Arrhenius law over the whole range of investigated parameters. The behaviour of the electrical conductivity of an electrolyte depends on the ZnSO 4 salt concentration. A continuous but very drastic decrease of the electrical conductivity is observed for compositions in isobutyric acid exceeding the critical composition. Comparing the electrical conductivity of electrolytic systems (IBA–W) + ZnSO 4 and (IBA–W) + KCl at a given salt concentration and IBA composition, one can note that the mobility of (K +, Cl −1) ions is greater than that of (Zn 2+, SO 4 2−) over the whole range of investigated parameters.

Evidence of Vogel–Tamman–Fulcher behavior in ionic binary fluids

The electrical conductivity σ of the six concentrated binary ionic mixtures of isobutyric acid–water with XM [KCl] at the critical concentrations was measured over an extended temperature range above the critical consolute point. Far from the critical temperature T c, the electrical conductivity is accurately described by the Vogel–Fulcher–Tammann (VFT) law. However, in a temperature range ΔT = T − T c ≤ 2 K, the electrical conductivity exhibits a monotonous deviation from the VFT behavior. This anomaly is finite at T c. The asymptotic behavior of the electrical conductivity anomaly is described by a power law (t)(1− α ), with t = (T − T c)/T c, the reduced temperature, and α the critical exponent of the specific heat anomaly at constant pressure. This critical anomaly is similar to the one observed in other different concentrated critical electrolytes. The degree of dissociation αdiss of the salt for the critical mixture is estimated from the value of the Walden product computed at T c. When the salt is added, the degree of dissociation αdiss shows dependence on the (K+, Cl−) concentrations: 0.15 < αdiss < 0.68.

Resistivity–viscosity relationship in liquid–liquid critical mixtures with added ions

Precise resistivity ρ (Ω cm) and viscosity η (10 −2 P) measurements for isobutyric acid–water (IBAW) critical mixtures with added K + and Cl − ions have been performed in the Arrhenius temperature domain of the electrolyte. From the activation energy, the resistivity–viscosity relation reveals a fraction power character over the whole range of parameters investigated. To analyze our data we have used an exponential formula derived from the equivalent Arrhenius law: ρ/ T is proportional to ( η/ T) R , where R = E ρ / E η is the ratio between the resistivity and viscosity activation energies. In the case of the pure system (IBAW), the value of R is in vicinity of 1, but when the salt is added, the ratio R shows dependence on the (K +, Cl −) concentrations: 0.6 < R < 1. The domain of the validity of R is in conformity with the theoretical prediction. The Coulombic interaction is the origin of the deviation.

Coexistence curves of electrical conductivity in critical solution: isobutyric acid–water with added ions

Comprehensive results of temperature (T) studies of electrical conductivity (σ) in the one-and-two phase regions of the binary fluid mixture of isobutyric acid–water (IBAW) with X M[KCl] at various critical concentrations are presented. A strong asymmetry of the coexistence curves as determined causes a strong violation of the law of rectilinear diameter. The obtained critical anomalies in the homogeneous phase σcrit (T) or the diameter of the σd (T) are associated with the same critical exponent θ = 1 − α ≈ 0.88, where α is the specific heat critical exponent. For the mixture with critical composition, the two phase regions show a concentration behavior with σl − σu ≈ |−t|β. The phase transition region shifts as a function of the salt concentration. The effective critical exponent β* = (0.264–0.296) is neither compatible with the Ising value β = 0.325 nor with the Fisher renormalized value ∼0.365.

Excess molar heat capacity of isobutyric acid–water binary liquid mixtures near and far away from the critical temperature

The heat capacity of the liquid–liquid mixture isobutyric acid–water has been measured for the first time near and far away from its critical point using an adiabatic calorimeter. The measurements were performed at atmospheric pressure, in the one phase region as a function of three temperatures: (1) T − T C = 0.055 °C, (2) T − T C = 3.055 °C, (3) T − T C = 8.055 °C and of the composition X in acid (IA). The heat capacity C p decreases rapidly when X increases at the used temperatures. Near the critical composition, C p is not affected by the correlation of the concentration fluctuations. The molar excess heat capacity of the system under investigation was analysed along the phase diagram and considered as a structural transformation effect.

Effect of the (K +, CL −) ions on the order parameters and on the Lorentz–Lorenz relation in the isobutyric acid–water critical mixture

The density ( ρ) and the refractive index ( n) in each phase of the critical binary fluid mixture “isobutyric acid–water” (I–W) with added (K +, Cl −) ions at various concentrations, were measured in the vicinity and far from the critical temperature. The obtained data were used to test the Lorentz–Lorenz (L–L) relation in this electrolyte system. The density and refractive index coexistence curve data were analyzed to determine the critical exponent β. The results show that the density ( ρ) and refractive index ( n) constitute good order parameters as valid as the volume fraction ( ϕ). Furthermore, the critical exponent β obtained for the pure mixture is in good agreement with theoretical predictions. The shift of the transition phase's area depends on the ion concentration. The Lorentz–Lorenz (L–L) is verified for all systems (I–W) and (I–W) + (K +, Cl −) ions. The relative deviation of the (L–L) relation is generally in the order of 7%, as well for the case of the pure system without ions, and in the presence of the ions with weak concentration.

Coexistence curves of the binary mixture isobutyric acid–water with added ions [formula omitted

Measurement of the coexistence curve of the binary mixture isobutyric acid–water (I–W) with increasing amounts of ions impurity showed essentially a linear dependence of the critical temperature and critical composition with concentration of (K +,Cl −) ions. Each coexistence curve of the electrolyte mixture is characterized by a new effective critical exponent β=(0.251−0.771) is neither compatible with the Ising value β=0.325. The experimental technique used here is the visual method.

Application of a novel-opposed-jets contacting device in liquid–liquid extraction

Liquid–liquid extraction of the recommended test system, cumene– iso butyric acid–water (CBW) as a typical example of liquid–liquid extraction processes has been carried out in a new two-opposed-jets contacting device (TOJCD). The experimental results clearly indicate that TOJCD provides much higher overall volumetric (capacity) mass transfer coefficients, K L a, than those of conventional extractors. This high overall volumetric (capacity) mass transfer coefficient, K L a, indicates greater performance capability of TOJCD relative to those of conventional contactors. In addition, the effects of the upper disk speed, solution flow rate, disk diameter, and the distance between disks on the extraction efficiency have been investigated. Furthermore, the effectiveness of two-opposed jets was evaluated by employing another new non-opposed-jets contacting device.