The knowledge of ion-solvent interaction by the help of volumetric and other fundamental properties has great importance and data generated from these experiments used for industrial applications. The experimental data of densities at 313.15K and 323.15K have been obtained for potassium dichromate (K₂Cr₂O₇) in 10% sucrose-aqueous solution measured as a function of their concentration. Experimental data of density evaluates the values of apparent molar volume, limiting apparent molar volume, experimental slope, molar volume and excess molar volume. The results were interpreted in the light of ion–ion and ion–solvent interactions and of structural effects of the solutes in solutions. These data give valuable information about interaction of compounds with carbohydrate which can be used for designing industrial and pharmaceutical applications.

Keywords: Molar volume; Excess molar volume; Sucrose

Carbohydrate chemistry is a sub discipline of chemistry primarily concerned with the synthesis, structure and function of carbohydrates. Potassium dichromate (K₂Cr₂O₇) is a crystalline ionic solid with a bright, red-orange color most commonly used as an oxidizing agent in various laboratory and industrial application. Basic and fundamental data are less available as far as carbohydrates are concern. The main objective is to provide data in binary system because substances interact differently then single system. Study in water-organic system not only important for industrial application as many chemical interact with both during processing and production which can affect the quality of products. It is also helpful in study of breakdown of carbohydrate which may help in research of drugs for many diseases like diabetes, obesity etc. Density is an example of an intensive property, a property in which the value is solely dependent upon the identity of the material, and not the amount present. Knowledge of volumetric properties to study in binary solvent system is useful for engineering design of new applications [1]. Sucrose solution plays an important role in biological and food industries. Sucrose has been the subject of structural and theoretical investigations for long time and research is still lively [2]. Since intensive properties are an inherent characteristic of the material they can be used to identify the material. Density data are required for many chemical engineering calculations involving fluid flow, heat and mass transfer [3]. The density of potassium dichromate (K₂Cr₂O₇) is studied in binary organo-aqueous solvent of sucrose-water. Potassium dichromate is used in cleaning, leather industries, photography and for construction purpose [2]. This study is done to investigate the interaction of potassium compound with sucrose solution because of biological importance of sucrose. Data of densities of potassium dichromate in sucrose-aqueous solution are scarce. The data of densities is used to analyse of apparent molar volume (fv), limiting apparent molar volume (ø_v), experimental slope (S*_v), molar volume (V) and excess molar volume (VE).

A stock solution of 0.10M of each of potassium dichromate is prepared in 10% (w/v) sucrose-aqueous solvent by direct weighing. Mass dilution technique is used for preparation of other concentrations. The concentration of the solutions involved in the experiment was taken in range from 0.01M to 0.10M. Densities of solutions of the potassium dichromate in sucrose-aqueous solvent are determined using 10cm3 double armed pycnometer at temperatures 313.15K and 323.15K. The pycnometer was calibrated at these temperatures with distilled water and benzene. The estimated accuracy of density measurement of solution was 0.00003g cm-3.

Density of potassium dichromate (K₂Cr₂O₇) is determined using equation [4],

$$\rho /{\rho }_1=W/W_1$$  (1)

Where, W and W₁ are weight potassium dichromate solution and weight of sucrose-aqueous solution respectively. r is density of potassium dichromate solution and r1 is density of sucrose-aqueous solution. Densities of dichromate solution are determined as a function of their concentration at 313.15K and 323.15K.

The densities of solute were obtained as an intercept of plot between concentration and density of solutions (using Microsoft Excel). The data is reported in Table 1. Apparent molar volume, Φ_v, is calculated by following the equation [5,6],

$${\varphi }_{\nu }=\left({\rho }_1-\rho \right)/c\rho {\rho }_1+M/\rho$$  (2)

Where, c is molarity of the solution, M is molar mass of the solute, r and r1 are density of solvent and solute. The result of fv of potassium dichromate is reported in Table 2.The apparent molar volume at infinite dilution (fov) were calculated by the method of least square and fit to plot of ∅fv vs c^1/2 in accordance with the Masson’s empirical relation [7],

$${\varphi }_v={\varphi }_v^0+S_v^{*}{c}^{1/2}$$  (3)

Where, $$S_v^{*}$$  is experimental slope. The slope is calculated by the extrapolation of the plots to zero concentration (using Microsoft excel). The positive values of experimental slope are generally associated with the solutes showing an overall hydrophilic character as in the present investigation. The values of apparent molar volume are reported in Table 2.

 The molar volumes of solutions are derived from the following expression [8,9],

$$V=\left(X_1{M}_1+X_2{M}_2\right)/\rho$$  (4)

Where, X1 and X2 are mole fraction of mixed solvent and mole fraction of solute. M1 and M2 molecular weight of solvent and molecular weight of solute r is density of solution respectively. The data of molar volume of solution is reported in Table 3. The molar volume of 10% (w/v) sucrose solution is 22.2116. The molar volume of potassium dichromate (K₂Cr₂O₇) is 280.9370 and 283.1376 at 313.15K and 323.15K respectively.

Knowledge of the excess molar volume is of important property in design and storage and handling facilities of mixtures .The excess molar volume (VE) for these solutions are obtained by the given expression [10,11],

$$V^E=V-\left(X_1{V}_1+X_2{V}_2\right)$$  (5)

Where, V, V1 and V2 are the molar volume of solution, mixed solvent and solute respectively. Negative excess molar volume arises due to increased interaction between the unlike molecules. The data of both the compounds are reported in Table 4.

The solutions generally do not behave ideally. The deviation from ideal behaviour is expressed by many thermodynamic properties, particularly by excess or residual extensive properties. Physical properties of liquid mixtures also affect most separation procedures, such as liquid-liquid extraction, gas absorption, and distillation. The data of densities increases as function of concentration. The positive value of fv indicates greater solute-solvent interactions. The values of f0v are large and positive for an potassium dichromate (K₂Cr₂O₇) in 10% (w/v) sucrose solution, suggesting the presence of strong solute–solvent interaction. The experimental slope of potassium dichromate is positive showing ion-ion interaction.