Temperature dependent study of viscosity has been employed for KNO 3 -NaNO 2 -NaNO 3 ternary molten salts using various empirical and statistical theories. The values derived are found to be in a fairly good agreement with the experimental values reported in the literature. Thus, the theories can be validated for its application to the multicomponent systems in general.

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Ultrasonic velocity (U), density (ρ) for the ternary mixture of (Toluene + Chlorobenzene + Cyclohexane) in the various range of composition has been carried out at 298.15K. The observed data have been utilized to calculate various acoustical parameters like Isentropic compressibility (KS), Intermolecular free length (Lf) and acoustic impedance (Z). The various excess properties like excess ultrasonic velocity(UE ), excess acoustic impedance (ZE ), excess Isentropic compressibility (KS E ) and excess Inter molecular free length (Lf E ) have been calculated and using standard relations to the Redlich-Kister equation. The trend of acoustical and physicochemical parameters confirm the dynamics of molecules at temperature and the magnitude of intermolecular interactions among the constituents of the mixture always reflects the nature of substance. The variations in sign and values of these parameters are help us to know the interaction between component molecules and structural arrangement of the liquid mixture.

The ground water is contaminated, its quality cannot be restored by stopping the pollutants from the source. The common pollutants of groundwater are discharge of agricultural, domestic, and industrial waste, pesticides etc., which leads to water- borne diseases. Water-borne diseases may be of microbial origin such as diarrhea, dysentery, cholera, typhoid and chemical origin such as flurosis and methemoglobinemia. Water Quality Index (WQI) provides a single number that expresses overall quality at certain location and time based on several water quality parameters. The objective of an index is to turn complex quality data in to information that is understandable and useable by the public. The present study was undertaken to assess the suitability of 8 drinking water sources of Doiwala block of Dehradun for drinking purpose during pre- and post-monsoon seasons of the year 2021. The obtained water quality data of drinking water sources was further applied for the calculation of weighted arithmetic Water Quality Index (WQI). Most of the water sources during pre-monsoon  season were  graded  as ‘A’ with  good  quality  due to having low WQI values. However, Two sites were found with ‘B’ class, another two were classified as ‘C’ grade owing to higher WQI values and thus, categorized as having poor water quality.  Two sampling sites were recorded with highest WQI value (59.29) and (68.24) its water quality was found poor for drinking purpose. During post-monsoon season, all analyzed water sources showed low WQI values, which indicates ‘A’ class i.e. excellent water quality. The higher WQI values during pre-monsoon season have been inferred owing to relatively higher calcium, magnesium and iron concentrations assessed during the period of study.

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