34;Volumetric and Viscometric Studies of Certain Binary and Ternary Sodium Dodecyl Sulfates (SDS) Containing an Alcohol System" was approved by the Board of Examiners in partial fulfillment of the requirements for Level M. The magnitudes of the VL values for the mixtures are in the order: isopropanol > methanol > ethanol > ii- propanol.
Properties of solutions
Therefore, there has been an interest in finding interconnections between the macroscopic properties of any system. The study of the physicochemical properties of binary and ternary mixtures attracted early attention from two main aspects.
Physical properties of alcohols
Since alcohols form hydrogen bonds with water, they tend to be relatively soluble in water. The hydroxyl group is referred to as a hydrophilic group, as it forms hydrogen bonds with water and increases the solubility of alcohol in water.
Surfactants
Water and alcohols have similar structural properties because water molecules contain hydroxyl groups that can form hydrogen bonds with other water molecules and with alcohol molecules and how wise alcohol molecules can form 1-I bonds with other molecules of alcohol, as well as with water molecules. Higher molecular weight alcohols tend to be less soluble in water, as the hydrocarbon portion of the molecule is hydrophobic ("water hating") in nature.
Classification of surfactants
Physical Properties of Surlactant Solutions
The reduction of the Gibbs free energy of the system, which is the result of the preferential self-association of the hydrophobic hydrocarbon chain of monomeric surfactant molecules, is the main reason for the formation of a micelle. Two main approaches, namely the phase separation model and the mass separation model, to the thermodynamic analysis of the micellization process have become widely accepted.
Factors affecting critical micelle concentrations
Prominent changes are influenced by those molecules (e.g. medium alcohols) which may be in the outer regions of the micelle. Micelles containing more than one surfactant are often readily formed with a CMC lower than either CMC of the pure components.
Structure of micelle
Organic molecules can affect CMCs at higher additive concentrations due to their influence of water structuring. Sugars are structure builders and cause a lowering of CMCs, while urea and formamide are structure breakers and their addition causes an increase in CMC.
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Structure of water
The introduction of a solute into liquid water causes changes in the properties of the solvent that are analogous to those caused by temperature or pressure. The concentration dependencies of the thermodynamic properties are a measure of solute-solute interactions and in the limit of infinite dilutions these parameters serve as a measure of solute-solvent interactions.
Hydrophilic hydration
The experimental result on various macroscopic properties provides useful information for a proper understanding of the specific interactions between the components and the structure of the solution. Accordingly, it is experimental data on various macroscopic properties (thermodynamic properties, viscosities, surface tension ctc) that provide useful information for a correct understanding of the specific interaction between the components and the structure of the solution.
THEORITICAL BACKGROUND
Physical Properties and chemical constitutions
When interpreting the composition, structure of molecules and molecular interactions in binary and ternary systems, it is inevitable to determine the size and shape of molecules and the geometry of the arrangement of their constituent atoms. Purely Constitutive Properties: A property that depends entirely on the arrangement of atoms in a molecule and not on their number is called a purely constitutive property.
Density
The density of a liquid can be determined either by weighing a known volume of the liquid in a density bottle or pycnometer or by buoyancy method based on "Archimedes principle". In our present investigation, the densities of the pure components and the mixture were determined by weighing a specific volume of the respective liquid in a density bottle.
Density and temperature
The absolute density of a given substance temperature t°C is equal to the relative density Ir multiplied by the density of Wale!' in temperature.
Molarity
Molar volume of Mixtures
The positive deviation in volume ie. volume expansion was explained by the breakdown of the mode of association by H-bonding of the associated liqs. The negative deviation in molar volume ie. Volume contraction has been thought by many observers to result from the i) compound formation by association, ii) decrease in the intermolecular distance between the interacting molecules, iii) interstitial accommodation of smaller species in the structural network of the larger species and (iv) change in the mass structure of any of the substances that make up the mixture.
Apparent/ partial molar volume
The concentration dependence of the apparent molar volume of electrolytes was described by the Masson equation (38), the Redlich-Mayer equation (40) and the Owen-Brinkley equation (39). For dilute solutions, the limit law for the concentration dependence of the apparent molar volume of electrolytes is given by the equation,
Viscosity of liquid mixtures
At low temperature the viscosity of a liquid is usually greater because the intermolecular attractive forces simply dominate the kinetic dispersive forces. At high temperatures, the kinetic energy of molecules increases at the expense of intermolecular forces, which decrease progressively. Therefore, the molecules of a liquid at high temperature offer less resistance to flow and thus less viscosity.
Viscosity also depends on pressure, molecular weight or mass of the molecule, molecular size and especially chain length, magnitude of intermolecular forces, such as association in pure liquids.
Excess viscosity measurements
Interaction parameter measurements, (c)
The jump of the moving molecules from one equilibrium position to the next can thus be considered equivalent to the passage of the system over a plot of energy barrier. AG# is the free activation energy per mol for viscous flow, V11, is the molar volume for pure liquids or solutions and h, N. The activation process to which AG refers cannot be described precisely, but in general terms it corresponds to the flow of the system.
For example, in normal liquids, the activation step may be the creation in the body of the liquid of a vacancy or holes into which an adjacent molecule can move. AH and AS4 are respectively the enthalpy of activation per mole for \'ISCOUS flow and AS4 is the entropy of activation.
Different thermodynamic parameters
- Free energy of activation (AG4) for viscous flow
- Enthalpy of activation (All4) for viscous flow
- Entropy of activation (AS) for viscous flow
Redlich-Kister equation
General Techniques
Preparation and Purification of Solvent
Apparatus
Methods (preparation of solution)
Conductance measurements
Density measurements
Apparent! Partial molar volume measurements
The partial molar volumes of the solute and solvent can be obtained from the density measurement using the following equation. The values of were obtained from the slope of the plot of (p vs. 'JJ using the Masson equation (38) and the apparent molar volume of solutes at infinite dilution ((° lz . V, °) were determined from the intercept of the plot , in C equal to zero.
Excess molar volume measurements
Viscosity measurements
Excess viscosity measurements
Interaction parameter measurements
Thermodynamic parametes
Coefficient Redlich-Kister equation and standard deviation
All the calculated excess properties, their corresponding polynomial coefficients and the standard deviation values are shown in the tables. In the figures, solid lines are drawn using the calculated excess property values using a computer program; whereas the symbols represent the corresponding experimental excess property values.
RESULTS AND DISCUSSION
Conductance and viscosity studies of SDS
For comparison, the densities of the pure components are shown in Table 4.3 together with the values from the literature. Interstitial accommodation of molecules of one component into the structural network of molecules of another component. Reorganization of pure components in mixtures due to the formation of diThrent types of weaker bonds and geometric mismatch or steric hindrance can also cause unfavorable packing and result in volume expansion.
The negative V' of the studied systems indicates that the factors leading to contraction upon mixing of the components dominate over the factors responsible for volume expansion. Results and discussion Chapter IV. but the orientation of groups, molecular sizes and shapes of components are also equally important.
Viscometric Properties
In the case of aqueous SDS solution, for prc-micellar or post-mus11ar region, no appreciable change of V has been observed. The viscosity of alcohol in water and SDS systems has been found to be in the order of . Compared to the alcohol-water association, the water-water association in the cage structure is believed to be more fragile to heat.
The level minima occurring at 0.9 mole fraction of alcohol as shown in the iso-Propanol (Figure 4.30) are seen to be somewhat prominent at lower temperatures. In the case of aqueous SDS solution, for pre-micellar or post-micellar region, it is seen that there is no significant change of viscosity or excessive viscosity after addition of SDS to the systems observed.
Thermodynamic properties
The values of viscous free energy (AG) at different temperatures are shown in Tables 4.32-4.39. The viscous free energy plot also indicates that micelle formation of SDS does not occur in the alcohol solutions studied. 4G' of alcohol in water and SDS systems has been found to be in the order of,.
The values of excess entropy of activation, 4SE for the investigated systems are shown in Tables 4.40-4.51. The values for excess activation enthalpy, LH for the investigated systems are shown in Tables 4.40-4.5 1.
Results (117(1 Disciissioiz Chapter IV Table 4.62: Coefficient, a, of Redlich-Kister equation expressing 4G and standard deviation, for the n-Propanol + Water, +0.005M SDS.
CONCLUSION
For measurements of volumetric, viscometric and thermodynamic properties, we considered two concentrations of SDS solutions as the pre-micellar region (0.005 M SDS) and the post-micellar region (0.01 M SDS). Studies on the solution properties of binary mixtures of methanol + water, ethanol + water, n-propanol + water and isopropanol + water and ternary mixtures of methanol + 0.005 M SDS and 0.01 M aqueous SDS, ethanol + 0.005 M SDS and 0.0 IM aqueous SDS. The values of excess molar volumes for all systems are negative and show minima in the water-rich region.
Although the value of density and viscosity of the studied systems in pre-micellar and post-micellar aqueous SDS solutions (0.005M SDS and 0.01M SDS) are higher than the pure water solutions, but no significant change in the volumetric and viscometric properties is observed by the addition of the surfactants. E Densities and excess molar volumes of methanol, ethanol and n-propanol in pure water and in water + Surf Excel solutions at different temperatures."
