Solubility and Metastable Zone Width
L-alanine Hydrogen Chloride (LAHC) salt was synthesized by taking L-alanine (99% purity) and analar grade HCl (98% purity) at the molar ratio of 1:1 in double distilled water. The dissolved solution was heated at 60oC for the synthesis of LAHC salt. The purity of the synthesized salt was further increased by repeated re-crystallization. Initially, the temperature was maintained at 30oC in the constant temperature bath. The re-crystallized sample of LAHC was added step by step to 50 ml of double distilled water in an air-tight container kept in the constant temperature bath and stirring was continued till a small precipitate was formed. This gave confirmation of supersaturated condition of the solution. Then 5 ml of the solution was pipetted out and taken in a petri dish and it was warmed up at 40oC till the solvent was evaporated out. By measuring the amount of salt present in the petri dish, the solubility (in g/100 ml) of LAHC in double distilled water was determined and this method of measuring solubility is known as gravimetrical method [8]. Metastable zone width (MSZW) is a basic and an important parameter in terms of temperature for growing a crystal by solution growth technique. In the present work, the metastable zone width of LAHC was measured by means of the conventional polythermal method [9]. Saturated solution of LAHC has been prepared in accordance with the solubility data. The studies were carried out in a constant temperature bath controlled to an accuracy of + 0.01 oC provided with a cryostat for cooling below room temperatures. A constant volume of 10 ml of solution was used in this experiment. The solution was preheated to 5oC above the saturated temperature for homogenization and left at the superheated temperature for 1 h before cooling. The equilibrium saturated solution was cooled from the overheated temperature and the temperature at which the first visible crystal nucleus in the solution was noted and this is the nucleation temperature. This experiment