A study of partial molar volumes of citric acid and tartaric acid in water and binary aqueous mixtures of ethanol at various temperatures

Abstract

Partial molar volumes of citric acid and tartaric acid have been determined in water and binary aqueous mixtures of ethanol (5, 10, 15, 20 and 25% by weight of ethanol) at different temperatures and acid concentrations from the solution density measurements. The data have been evaluated by using Masson equation and the obtained parameters have been interpreted in terms of solute-solvent interactions. The partial molar volumes vary with temperature as a power series of temperature. Structure making/breaking capacities of the organic acids have been inferred from the sign of [∂ 2 φv 0 /∂T 2 ] p , i.e. second derivative of partial molar volume with respect to temperature at constant pressure. Both the organic acids behave as structure breakers in water and water + ethanol.

Studies of Partial Molar Volumes of Some Narcotic-Analgesic Drugs in Aqueous-Alcoholic Mixtures at 25°C

“…Furthermore, it has also been observed that these values are independent of the nature of the drug. Similar observations have been reported by Parmar et al [14] for ammonium, sodium, and potassium phosphates in binary aqueous solutions of urea, and for citric acid and tartaric acid [15] in water and binary aqueous mixtures of EtOH at various temperatures in which S v values are reported to be negative. Also, for a number of hydrochloride-type drugs, either negative or very small values of S v have been reported in the literature [16], indicating weak ion-ion interactions.…”

“…Therefore, an appreciable inter-ionic penetration occurs and gives rise to negative slopes which leads to weak ion-ion interactions and strong ion-solvent interactions. These negative values of S v for different compositions also suggest the presence of cation-anion penetration [14,15], and this happens due to the competition between the drug ions to occupy the void space of the large solvent molecules. Also, it is seen (Tables 5-8) that there is no appreciable variation in S v with a change in composition of a particular aqueousalcoholic system, even when the alcohol component changes from MeOH to 1-PrOH.…”

Volumetric, ultrasonic speed, and viscometric studies of salbutamol sulphate in aqueous methanol solution at different temperatures

“…Similar observations were reported by Parmar et al [28] of citric acid and tartaric acid in binary aqueous mixtures of ethanol at various temperatures using the negative S v values. However, at a particular temperature, with the increase of methanol content in aqueous methanol solution, V 0 / increases there by showing that solute-solvent interactions improve on the addition of more and more methanol in water [28]. From table 3, it is seen that the values of partial molar expansivity E 0 2 are positive indicating that the drug is a structure maker [29].…”

“…This is attributed to the fact that in a solvent of high dielectric constant like water, the solutes remain completely ionised even at fairly high concentration [27]. Similar observations were reported by Parmar et al [28] of citric acid and tartaric acid in binary aqueous mixtures of ethanol at various temperatures using the negative S v values. However, at a particular temperature, with the increase of methanol content in aqueous methanol solution, V 0 / increases there by showing that solute-solvent interactions improve on the addition of more and more methanol in water [28].…”

Interaction Studies of Dilute Aqueous Oxalic Acid

“…The concentration range used in the study was optimum for the validity of Staurdinger, Jone-Dole equation and Modified Jone-Dole equation in which it acts as structure maker. Further addition of solute can modify the structure of water by hydration as obtained volumetrically 10,11 from thermal expansion. The ratio of (B x /B) is 53.31, which is nearly equal to reported value for sugars 1 .…”