Volumetric and transport properties of betaine hydrochloride drug in aqueous uracil solutions at T = (298.15–318.15) K Abhijit Sarkar, Bijan Kumar Pandit, Biswajit Sinha ⇑ Department of Chemistry, University of North Bengal, Darjeeling 734013, India article info Article history: Received 13 January 2016 Received in revised form 21 February 2016 Accepted 3 March 2016 Available online 11 March 2016 Keywords: Partial molar volume Viscosity B-coefficient Betaine hydrochloride Aqueous uracil solution abstract Apparent molar volumes and viscosity B-coefficients for betaine hydrochloride in aqueous uracil solutions were determined from solution densities and viscosities measured at T = (298.15–318.15) K and at pressure p = 101 kPa as a function of betaine hydrochloride concentrations. The standard partial molar volumes / 0 V   and slopes S  V   obtained from Masson equation were interpreted in terms of solute–solvent and solute–solute interactions, respectively. Solution viscosities were analyzed using Jones–Dole equation and the viscosity A and B coefficients discussed in terms of solute–solute and solute–solvent interactions, respectively. The standard volume of transfer D t / 0 V   and viscosity B-coefficients of transfer ðD t BÞ of betaine hydrochloride from water to aqueous uracil solutions were derived to understand various interactions in the ternary solutions. The activation parameters of viscous flow for the studied solutions were discussed in terms of transition state theory. The structure making or breaking ability of betaine hydrochloride was discussed in terms of the sign of d/ 0 E =dT   P . Ó 2016 Elsevier Ltd. All rights reserved. 1. Introduction Volumetric and viscometric properties provide valuable infor- mation regarding the behaviour of various solutes such as proteins, peptides, drugs, nucleotides, carbohydrates in aqueous or non- aqueous media [1–8]. Understanding the action of drugs and their interaction with different biologically important compounds is a subject of research interest. These interactions provide idea about the activity of drug in biological systems. As the drug action is dif- ficult to understand, different thermodynamic and rheological properties such as density and viscosity are used to interpret the drug-macromolecule interactions. Betaine hydrochloride drug (B.HCl) is used for supplementing low stomach acid which is a key component of our immune system and it is also used as a digestive pill for the human body. In some cases it may also used for the treatment of food allergies, diarrhoea, thyroid disorder and low level of potassium. Uracil is one of the four nucleobases in the nucleic acid of RNA. It helps the body to synthesize many enzymes necessary for cell functioning. It is also used as a allosteric regulator in the body. It can be used for drug delivery. It is therefore interesting to observe the interaction between B.HCl and uracil in aqueous media. Many studies on the thermodynamic and rheological properties of drugs have been carried out by a number of researchers [8–13]. Gardas et al., studied the acoustic and volumetric properties of betaine hydrochloride drug in aqueous glucose and sucrose solu- tions [14]. To the best of our knowledge from the literature survey, the values of density and viscosity of B.HCl drug in aqueous uracil solutions have not been reported at the concentrations and temperatures investigated in this article. Hence the purpose of the present work is to study the various interactions interplaying in the aqueous solutions of B.HCl drug and uracil in terms of apparent molar volumes, standard partial molar volumes and viscosity B-coefficients, etc., at T = (298.15–318.15) K under atmospheric pressure. 2. Experimental 2.1. Materials Betaine hydrochloride, [(CH 3 ) 3 NCH 2 COOH] + Cl  (CAS: 590-46- 5; Sigma Aldrich, mass fraction purity >0.990) and premium grade Uracil, C 4 H 4 N 2 O 2 (CAS: 66-22-8; Sigma Aldrich, mass fraction pur- ity >0.990). Betaine hydrochloride and uracil were used without further purification but they were dried in vacuo over anhydrous CaCl 2 for several hours before use. Provenance and purity of the chemicals has been given in Table 1. Deionized doubly distilled degassed water with a specific conductance <10 6 S cm 1 was used http://dx.doi.org/10.1016/j.jct.2016.03.008 0021-9614/Ó 2016 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: biswachem@gmail.com (B. Sinha). J. Chem. Thermodynamics 98 (2016) 118–125 Contents lists available at ScienceDirect J. Chem. Thermodynamics journal homepage: www.elsevier.com/locate/jct