The values of the limit of apparent molar volume expansions (Eφ0) are positive and the values of (δEφ0/δT)p are small making the structure representing property in these systems. The changes of free energies (ΔG#) are increased with the increase in concentration of paracetamol and the values are positive for all the studied systems.
General
Properties of solute in solvent
Theoretically, the solute-solvent interactions that imply the properties of solutions can be calculated from the properties of the individual components. Solution theory is still far from being adequate to account for solution behavior in terms of the properties of the constituent molecules.
Properties of Paracetamol
Paracetamol is part of the class of drugs known as "aniline analgesics"; it is the only such substance still in use today. Paracetamol can relieve pain in mild arthritis, but has no effect on the underlying inflammation, redness and swelling of the joint.
Properties of alcohols
The oxygen atom of the strongly polarized O-H bond of an alcohol removes electron density from the hydrogen atom. Alcohols with five or more carbons (Pentanol and higher) are effectively insoluble in water due to the dominance of the hydrocarbon chain.
Properties of Water
Structure of water
The introduction of a solute into liquid water produces changes in solvent properties that are analogous to those caused by temperature or pressure. Concentration dependences of thermodynamic properties are a measure of solute-solute interaction, and in the limit of infinite dilutions these parameters serve as a measure of solute-solvent interactions.
Hydrophilic hydration
The thermodynamic and transport properties are sensitive to the interactions between solute and solvent, solute and solvent. Dissolution of any solute will disrupt the arrangement of water molecules in the liquid state and create a hydration shell around the solute.
Hydrophobic hydration and hydrophobic interaction
If the solute is an ionic species, this hydration shell is characterized to extend from an inner layer where water molecules near the charge species are strongly polarized and oriented by the electrostatic field, through an intermediate region where water molecules are significantly polarized but not not strong oriented, to an outer solvent region of bulk water where the water molecules are only slightly polarized by the electric field of the ion (21).
Paracetamol-Solvent systems
The effect of paracetamol in aqueous sodium malonate solutions has also been measured using volumetric and viscometric measurements (27). The physicochemical properties of paracetamol and aspirin in a water-ethanol system were also investigated (32).
The object of the present work
We therefore decided to study the density and viscometric properties of paracetamol in the mixed solvent system. As far as we know, there are no complete data of density, viscosity and molar properties of paracetamol in aqueous solution of n-Propanol, n-Butanol, at prolonged temperatures.
Physical Properties and chemical constitutions
An additive property is one which, for a given system, is the sum of the corresponding properties of the constituents. There are other molecular properties such as molar volume, radioactivity, etc. are highly additive in nature. ii) Purely constitutive properties: The property which depends solely on the arrangement of the atoms in the molecule and not on their number is said to be a purely constitutive property.
Density
The relative density of a substance is the ratio of the weight of a given volume of the substance to the weight of an equal volume of water at the same temperature (d104). 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".
Density and temperature
Theoretical background Chapter II. at 40C), the density of water at this temperature is expressed in gmL-1 unit and the density of water at any other temperature is expressed relative to that of water at 40C and expressed by (d104). The absolute density of a certain substance temperature t0C is equal to the relative density multiplied by the density of water at that temperature.
Molarity
In our current study, the densities of the pure components and the mixture were determined by weighing a certain volume of the liquid of interest in a density flask.
Molar volume of Mixtures
Theoretical background Chapter II. 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 bulk structure of one of the substances forming the mixture.
Apparent/ partial molar volume
The concentration dependence of the apparent molar volume of electrolytes has been described by the Masson equation (50), the Redlich-Mayer equation (52) and the Owen-Brinkley equation (51). For dilute solutions, the limiting law for the concentration dependence of the apparent molar volume of non-electrolytes is given by the equation,
Viscosity
For dilute solutions, the limiting law for the concentration dependence of the apparent molar volume of non-electrolytes is given by the equation, and for not very low concentrations, the concentration dependence can be represented as, . i) contact area 'A' between the two layers and (ii) velocity gradient. When a liquid flows through a narrow tube, it is likely that the thin layer of liquid in contact with the wall is stationary; as a result of viscosity, therefore, the next layer will slow down to some extent and this effect will continue to the center of the pipe where the flow velocity is maximum. The rate of flow of liquid under a given pressure will obviously be less the smaller the radius of the pipe, and the relationship between these quantities was first obtained by J.L.M.
The driving pressure P = hρg, where h is the difference in the height of the surface of the two reservoirs, since the external pressure is the same at the surface of both reservoirs, g = acceleration due to gravity andρ= density of the liquid. By putting the value of and of the experimental liquid/solution and the value of the viscometer constant A into equation (2.33), the viscosity coefficient can be obtained for a liquid at a certain temperature.
Viscosity and temperature
2 at the experimental temperature and by measuring the flow time of water, the calibration constant A for a given viscometer can be determined. Therefore, at high temperatures, the molecules of a liquid offer less resistance to flow and therefore less viscosity. Viscosity also depends on pressure, molecular weight or mass of the molecule, molecular size and especially chain length, and the magnitude of intermolecular forces, such as association in pure liquids.
Viscosity of liquid mixtures
Viscosity as a rate process
Assuming that ΔH# and ΔS# are almost independent in the temperature range studied, a plot of lnVm/Nh against 1/T will give a straight line with slope.
Different thermodynamic parameters
General Techniques
Materials
Preparation and Purification of Solvent
Apparatus
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.
Transfer apparent molar volume of measurements
Temperature dependent limiting apparent molar volume measurements
The inside of the viscometer was thoroughly cleaned with warm chromic acid and then with distilled water, so that there was no blockage in the capillary and the liquid could flow freely without leaving any drop. The viscometer was then clamped vertically in the thermostatic water bath so that the top mark of the upper bulb was well below the water level. Using a pipette filler attached to the narrower part of the viscometer, the water was aspirated above the top mark of the bulb.
Since the exact viscosity and density of water at different temperatures are known (from the literature), the calibration constant A of the viscometer for different temperatures was obtained by using Eq. By setting the values of the calibration constant, density and flow of the experimental solution, the viscosity of this solution was determined using equation 3.40.
Coefficient B and D determinations
Thermodynamic parameters
Although the complete theory of the B coefficient is not known, it has long been used by workers to explain the interaction between ions and solvent molecules. The study of the B-coefficient is very important for the qualitative determination of the effects of ions on the structure of solvents. According to Feakins, Freemantle and Lawrence's coefficient B are related to the difference in chemical potential for the flow of one mole of solution with concentration C and solvent with the ratio (59).
Experimental results and properties derived from experimental data are presented in this section. The information obtained about these systems is presented in different sections and discussed in the light of the theories mentioned in the previous chapter.
Volumetric Properties
It shows that densities increase with the increase in concentration of paracetamol and decrease with temperature. The apparent molar volumes increase with the increase in concentration of paracetamol and also with increase in temperature. The observed positive values of Δφv indicate strong solute-solvent interactions of paracetamol with aqueous alcohol solution through H-bonding.
Apparent molar volumes (φv) were found to correlate linearly with solution concentration (C) at all experimental temperatures, so standard partial molar volumes (φv0) were obtained from Masson's equation (50). Section (φv0), i.e. the partial molar volume provides a measure of solute–solvent interactions, and the SV slope provides information on solute–solvent interactions (63). The observed positive values of Δφv0 indicate strong solvent–solvent interactions of paracetamol and the aqueous alcohol solution.
Viscometric Properties
The positive and small negative values of (δEφ0/δT)p for the studied systems show the structural ability of paracetamol in all aq. In the presence of paracetamol, viscosity values generally decrease with increasing percentage of water in the mixed solvent. This may be due to the interaction between water molecules and alcohols through H-bonding (73). b) The viscosity value increases with increasing paracetamol concentration.
It is seen that the ΔG# values of paracetamol in aqueous solutions of n-Propanol and n-Butanol increase very slowly with increasing solute concentration and decrease with increasing temperature (Fig. This shows that the value of enthalpy increases with the increase in concentration of paracetamol and the value of entropy decreases with the increase in concentration of paracetamol for most of the systems The apparent molar volumes (φv) of Paracetamol are determined from density data and the values of φv are found to be positive and increase with the increase in concentration of paracetamol.
Thus, the above experimental results demonstrate the structure-forming properties of paracetamol in a solution of water and aqueous alcohols.
