Single crystals of ammonium nickel sulphate, potassium nickel sulphate, ammonium alum and potassium alum are grown in sodium-metasilicate gels. The method of gel preparation and growth procedure are described. Both single diffusion and double diffusion methods are used. Studies on nucleation and characterisation of crystals are also reported. Crystals grown are illustrated.

The experimental conditions for obtaining periodic crystallization of barium oxalate in silica hydrogel are investigated. The Liesegang rings formed by the reaction of oxalic acid and barium chloride are studied. The dependence of velocity constant and the spacing coefficient on pH, concentrations of inner and outer electrolytes and temperature have also been studied and a possible mechanism for the behaviour is suggested. The deviations from Isemura’s general observations are interpreted by considering the microcrystals constituting the rings and the irreversibility of inner and outer electrolytes.

Etch pits produced by selective etchants such as 1 M HCl, 1 M HNO₃, 4 M BaCl₂, 4 M NH₄Cl and 4 M NH₄Cl-1 M HCl solutions on the as-grown {110} faces of barium oxalate dihydrate crystals are illustrated and explained. The kinetics of etching is studied. From Arrhenius plots, the activation energy of etching and the pre-exponential factor are computed. An empirical equation governing the kinetics has been suggested.

The kinetics and thermodynamics of the thermal dehydration of crystalline powders of BaC₂O₄·2H₂O, CdC₂O₄·3H₂O and Ba_1−xCd_xC₂O₄·2·5H₂O have been studied by means of thermogravimetry, as a function of temperature. The dynamic dehydration kinetics are also examined using DTA, recorded simultaneously with TG as a function of temperature. The validity of the estimated mechanism and kinetic parameters is briefly discussed. From DTA study it is concluded that all dehydration peaks are endothermic and the decomposition peaks of barium oxalate to barium carbonate, cadmium oxalate to cadmium oxide and barium cadmium oxalate to barium carbonate and cadmium oxide are exothermic.

Characterization of the gel-grown barium hydrogen phosphate (BHP) crystals was performed by utilizing the techniques of chemical analysis, X-ray diffraction, infrared and thermal behaviour. The results show that BHP crystals had chemical composition BaHPO₄ at room temperature. TG and DTA studies revealed the BHP crystals to be anhydrous at room temperature and decomposed at temperatures above 370°C and the decomposition was an endothermic process. Magnetic susceptibility measurements indicate the material to be diamagnetic.

Barium copper oxalate was grown in silica hydrogel at ambient temperature. The effect of various parameters like gel pH, gel density, gel aging and concentrations of reactants on the growth of these crystals was studied. The crystals grown were characterized by chemical analysis, X-ray powder diffractometry, infrared spectroscopy, thermogravimetric and differential thermal analysis. The results of these observations are described and discussed.

The present paper reports observations made on microstructures of gel-grown barium copper oxalate crystals. Growth spirals, growth layers, liquid inclusions and growth of microcrystallites are described and discussed in relation to the mechanism and conditions of crystal growth.

Aspects of gel growth of cadmium oxalate single crystals doped with monovalent (Li⁺, Na⁺, K⁺ and NH₄⁺) and divalent (Ca²⁺, Co²⁺, Ni²⁺ and Zn²⁺) cation impurities are discussed. The growth experiments were carried out by single diffusion method. In this paper the effect of composition of the supernatant solution is considered. Rigorous characterization involves determination of composition of cations by employing atomic absorption spectrophotometer and of anions by titration method. The Pauling radius, hydration energy and distribution coefficient of the cations are tabulated and the results are described and discussed.

Implantations were carried out on gel-grown potassium dihydrogen orthophosphate (KDP) and those doped with magnesium oxide (MgO) single crystals using 100 MeV Ag⁺ heavy-ion beam of 15 UD 16 MV pelletron accelerator. To conduct a comparative study, measurements were carried out in the temperature range 243 K-403 K at frequencies ranging from 1 kHz-1 MHz on irradiated and nonirradiated nonlinear samples. It was observed that the mechanism of dielectric behaviour varied with frequency, temperature and ion irradiation. Further, implantation produced erratic variation in the conductivity both in the intrinsic and extrinsic regions, and also in the dielectric behaviour of the substance. The property of sensitive dependence on initial conditions, namely, chaos had set in after ion irradiation. However, the doping effect had not completely terminated the above transition, leading to chaos in the nonlinear medium.