Optik 124 (2013) 4614–4617 Contents lists available at ScienceDirect Optik j o ur nal hom epage: www.elsevier.de/ijleo Investigation on sodium potassium bitartrate crystals grown in silica gel and its characterization V. Mathivanan a,b , M. Haris a,∗ a Department of Physics, Karunya University, Karunya Nagar, Coimbatore 641 114, Tamil Nadu, India b Department of Physics, United Institute of Technology, Coimbatore 641 020, India a r t i c l e i n f o Article history: Received 11 September 2012 Accepted 20 January 2013 Keywords: Gel technique Sodium potassium bitartrate FTIR Powder XRD Magnetic moment and thermal properties a b s t r a c t The single-crystal growth of sodium potassium bitartrate by controlled diffusion in silica gel is reported. The influence of growth parameters, e.g. reactant concentrations, gel pH, gel aging on the size and nuclea- tion density of crystals has been studied. Operative mechanisms of crystallization, results of growth kinetics and morphology of crystals are discussed. The energy dispersive X-ray analysis (EDAX), Fourier transform infra red (FTIR) spectroscopy, powder X-ray diffraction (XRD), magnetic properties and Ther- mal analysis (TGA/DTA) have been made to find the stoichiometric composition of the crystals and its structure. © 2013 Elsevier GmbH. All rights reserved. 1. Introduction Crystal growth in gels has made remarkable progress in the recent years. With the advent of extensive work by Henisch and co-workers [1,2], gel growth research has made rapid strides in the field of crystal growth in general, and the growth of materials in gel in particular. The importance of gel growth can be visualized by the fact that a number of researchers have started to develop crys- tals of technological potential by this method [3–8]. Another factor arousing interest in this type of growth is that crystals of various sorts of ionic, organic and even metallic can be grown at ambient temperatures. Growth kinetics which is so vital in understanding the growth mechanisms in this type of growth has also been dealt with extensively [1,9–16]. It is pertinent to point out here essentially no work has been reported so far on the gel growth of sodium potassium bitartrate crystals. We report here the growth of sodium potassium bitartrate in gel medium. The growth mechanism and characterization of the grown crystals are described and discussed. 2. Experimental procedures The crystallization apparatus for the growth of sodium potas- sium bitartrate consist of glass tube of length 20 cm and diameter 2.5 cm placed vertically on plastic stand. Silica gel was prepared by ∗ Corresponding author. Tel.: +91 9841848926; fax: +91 422 24615615. E-mail address: harismuthiah@karunya.edu (M. Haris). acidifying pure sodium meta silicate (Na 2 SiO 3 ) of specific gravity 1.05 g/cm 3 , with tartaric acid of a concentration in accordance with the requirements of a particular pH value. The tartaric acid solution was added slowly to sodium metasilicate solution with continuous stirring to avoid any local ion concentration which would otherwise cause premature local gelling and make the final solution inho- mogeneous. Here, tartaric acid acted as a lower reactant. A fixed amount of gel solution with the desired value of pH was then trans- ferred to several test tubes. The test tubes were sealed with cotton to prevent fast evaporation and contamination of the exposed sur- face of the gel. The gel solution was allowed to set. The setting of gel is strongly dependent on pH. High pH value gel takes lower time to set than the low pH value. After confirming the gel setting, an aque- ous solution of NaCl and KCl of required concentration was poured slowly along the sides of the test tube, to prevent the breaking up of gel surface. Slow diffusion of the upper reactants ions through the narrow pores of the silica gel leads to the reaction between these ions and the ions present in the gel as lower reactant. The following reaction was expected inside the gel xNaCl + (1 - x)KCl + C 4 H 6 O 6 → Na x K (1-x) HC 4 H 4 O 6 + HCl (x = 0.7, 0.6, 0.5, 0.4, 0.3) The grown crystals of sodium potassium bitartrate are shown in Fig. 1. The details of experiments for the growth of sodium potas- sium bitartrate are shown in Table 1. With appropriate boundary conditions Fick’s law, in the case of one-dimensional diffusion, gives the rate of growth of the crystal in 0030-4026/$ – see front matter © 2013 Elsevier GmbH. All rights reserved. http://dx.doi.org/10.1016/j.ijleo.2013.01.101