Study of Optical Property of Gel Grown Mercuric Iodate Crystals

Abstract

Mercuric Iodate Crystals were grown by a simple gel technique using diffusion method. The optimum growth conditions were established for the growth of these crystals by changing various parameters such as pH of the gel solution, gel concentration, gel setting time, concentrations of reactants etc. The grown Mercuric Iodate crystals were spherical in shape. These crystals were opaque. The crystals were characterized using UV- VIS Specrophotometrry. .Keywords. Gel technique, mercuric iodate crystals, UV-VIS Specrophotometrry. I. Introduction: A variety of crystals required for the purpose of research and application can be grown in silica gels. The gel medium prevents turbulence and being chemically inert, it provides a three-dimensional crucible which permits the reagents to diffuse at a desirable controlled rate. Its softness and uniform nature of constraining forces that it exerts upon the growing crystals encourages orderly growth. The growth of single crystals in gel at an ambient temperature, which are sparingly soluble in water, is a fascinating alternative to the techniques involving high temperature and expensive equipments. During the last few years, successful application of gel growth technique has been demonstrated by the preparation of single crystals of alkaline earth metal iodate. The gel growth technique appeared quite attractive for growing crystals of such compounds on account of its unique advantages in terms of crystals produced and the simplicity of process. In the present work, crystals of mercuric iodate were grown by gel technique using diffusion method. Optimum growth conditions for crystals were determined. Optimum conditions were established by varying various parameters. II. Materials and Method Test tubes were used as crystallizing vessels. The silica gel was used as a growth media. Gel was prepared from aqueous solution of sodium meta silicate. The gel was acidified by acetic acid. The chemicals used for growth of single crystals of mercuric iodate were CH3COOH; Na2SiO3.5H2O; KIO3, NaIO3; Hg(NO3)2. All chemicals were of AR grade. A series of experiments using different pH values for the gel and the different concentrations for reactants were carried out. Different molar masses were tried to determine the optimum growth conditions. Out of the two reactants, Hg(NO3)2 was incorporated in gel and KIO3 was used as the supernatant over the set gel. These experiments yield spherulitic crystals of Hg(IO3)2 of few mm size. Experiments were also carried out by interchanging the position of reactants. These experiments do not yield any crystals at all. Hg(NO3)2 having different concentrations was incorporated into the gel. This solution was then transferred to borosil glass tube of diameter 2.5 cm and 25 cm in height. The mouth of the tube was covered by cotton plug. After setting of the gel, it was left for aging for different periods of time. Another reactant having different concentrations was then added as supernatant over the set gel. Experiments were carried out by changing different concentrations of the reactants. The chemical reaction inside the gel can be expressed as X(NO3)2 + 2YIO3 → X(IO3)2 + 2YNO3 Where X = Hg and Y = K or Na