The growth of vitamin C single crystals was studied by direct observation In flowing solution, the linear growth rates of three orientations (, , ) were measured for vitamin C water system The experiments were designed as orthogonal test to investigate the effect of various factors Comparing with temperature and velocity, supersaturation is the most important factor And the relations between growth and supersaturation were different with crystal directions, which obviously show anisotropy The order of magnitude of G , G , G and their dependency on supersaturation ( g , g , g ) were in good agreement with analysis of maximum difference The effect of solution diffusion could be neglected and crystal growth was controlled by surface reaction According to the growth models, the growth mechanism was
The experiments of single crystals growth for vitamin C were carried out on growth rates of different orientations (,and ).Under various temperatures and supersaturations, the directional growth rates were measured The kinetic parameters were regressed by the least square method and verified by significance test In aqueous and ethanol aqueous solution, the kinetic parameters changed greatly, and the controlling step of growth differed from each other So crystals in aqueous solution are often in rod form,while always in plate form in water ethanol The effects of solvent on directional growth were analyzed according to steric effect of solvent molecules and hydrogen bond interaction at solution crystal
The single crystal growth rates of potassium sulfate in pure aqueous solution under different conditions were determined by photomicrography in a flow system for crystal growth. The effects of the main controlling factors, such as supersaturation, crystal size, solution velocity and crystal growth temperature, on crystal growth rates of potassium sulfate were discussed in detail by using non-linear regression from the experimental data, and several empirical relationships were given.The results showed that the growth rates of crystals increased with supersaturation, crystal size, solution velocity and temperature. Moreover supersaturation was the most important controlling factor influencing growth rates of crystals,crystal size and solution velocity were the secondary and temperature was the least. Furthermore, It was found that the growth rate of crystals along the crystallographic axis was higher than that along the in the same condition. The effect of every factor on crystal growth rates along the crystallographic axis was stronger than that along the .
