A simple spectrophotometric method is developed for the determination of phosphate in sugar cane juice, water and detergent samples. The method is based on the formation of phosphomolybdate with added molybdate followed by its reduction with sodium sulphide in aqueous sulfuric acid medium. The system obeys Lambert-Beer’s law at 715 nm in the concentration range 0.3-12.24 ppm. Molar absorptivity, correlation coefficient and Sandell’s sensitivity values were found to be 6.1x103mol-1cm-1, 0.999 and 0.0156 µg cm-2respectively. The results obtained were reproducible with acceptable standard deviation 3.7% and relative error 3.4%. For a comparison of the method phosphate present in various samples were also determined separately following an official method. The results of the developed method compare well with those of the official method.

1 volumetric [6, 19] as well as other methods [12-16] when sulfur dioxide is in low concentrations, because of its simplicity and cost-effective instrumentation. However, one of the spectrophotometric methods [20] employs rosaniline and formaldehyde, which are considered to be toxic [21]. Another AOAC method [22] requires the use of the dye thymol blue, a known pH indicator. Obviously, the method requires the strict control of pH and also suffers from a narrow range of sulfur dioxide determination. Therefore, a new spectrophotometric method for sulfur dioxide is developed in our work. The method is based on the formation of a redbrown peroxovanadate complex [23-25], λ max = 470 nm, from ammonium metavandate and hydrogen peroxide in 2 M sulfuric acid. When sodium metabisulfite (Na 2 S 2 O 5 = 2SO 2) is added, it preferentially reacts with hydrogen peroxide, thereby decolorizing the peroxovanadate complex until its concentration is less than that of the complex.

A novel, simple, sensitive spectrophotometric method is proposed for the determination of five phenothiazines. Chloramine-T with iodine in acetic acid produces iodine monochloride which oxidizes phenothiazines to absorbing cations. Those would associate later with unreacted ICl to form an ion pair, [Ph+] [ICl-(2)] in hydrochloric acid medium. These appear to provide exceptional color stability to the systems. A probable mechanism along with experimental stoichiometry and stability constants of such ion pairs is indicated. The method is not only successful in stabilizing the color of the systems, but also in making a unique observation of two regions of concentration of phenothiazines adhering separately to Beer's law. The results obtained from the analyses of pure samples and their drug formulations in both regions of concentration are comparable with those obtained either with a reported titrimetric method or with a British Pharmacopoeia (B.P.) UV-spectrophotometric method. The conditions required for the quantitative determination of phenothiazines are described and related analytical parameters are also calculated.

A simple, sensitive and economical spectrophotometric method for the determination of hydrogen sulphide is developed. The method is based on a redox reaction in that Mn(III) generated electrolytically is taken in excess, which is oxidizing a known but a less quantity of hydrogen sulphide and the unreacted oxidant will oxidize furthero-tolidine to produce an orange yellow quinonediimine absorbing cation (λ max. 455 nm). Therefore, in principle, the decrease in color intensity of the absorbing system is proportional to the concentration of hydrogen sulphide. The stoichiometry between Mn(III) ando-tolidine and stability constant of the complex were determined by Job's continuous method, the corresponding values were found to be 2:1 and 1.42X105Lmol-1. The system was obeying Lambert-Beer's law in the range 0.2-1.4 μg mL-1of hydrogen sulphide. Molar absorptivity, correlation coefficient and Sandell's sensitivity values were also calculated and found to be 4.2062X103L mol-1cm-1, 0.999 and 0.0012 μg cm-2respectively. The method was employed for the determination of hydrogen sulphide in water samples. The results obtained were reproducible with acceptable standard deviation 0.01-0.068 and relative standard deviation, less than 3.21%. For a comparison, hydrogen sulphide present in water samples were also determined separately following the methylene blue official method. The results of the proposed method compare well with the official method.

In this work, acoustic, thermal, and optical properties were tested on the different concentrations of the Disodium Tartrate solutions. First, the viscosity studies were analyzed for the Disodium tartrate in the concentration range from 2% to 20% with different temperatures 303K, 308K, 313K, and 318K. It was noted that the relative viscosity and the activation energy of the prepared compound increase with increases in concentration and decreases with temperature increases. The properties like density and ultrasonic velocity are varied when increases the concentration of the aqueous solutions of Disodium Tartrate. In this study, the values of adiabatic compressibility show an inverse behavior when compared with ultrasonic velocity due to the interaction between solute and solvent molecules. Also observed that the inter-molecular free length is maximum for a lower percentage. The free volume for the compound is maximum at 2% and a minimum of 20%, since it reduces when the internal pressure increases. It was revealed that the classical absorption coefficient and relaxation time for Disodium Tartrate is minimum for lower percentage and minimum for a higher percentage. The interactions between the solute and solvent are confirmed through the property like specific Acoustical impedance. It was noted that the increase in internal pressure increases the concentration of the compound. The ion-solvent interaction was discussed by the relative association study, thus the values of relative association increases with an increase in concentration. The Rao’s and Wada’s constant increases linearly in aqueous solutions of Disodium Tartrate for the entire system.