Sucrose crystal hardness: a correlation with some parameters defining the growth kinetics

The experimental appearence of facets of crystallographic forms on the surface of sucrose apherical single crystals fits well the decreasing order of their absolute rates under the same experimental conditions. The validity of this relationship is also confirmed: (a) by experimental sphere growth from solution doped with raffinose where the appearence sequence is inverted since the impurity inverts the order of absolute rates; (b) by the holographic analysis of the gowth of non polar <hkl> zone of sucrose cylindric single crystals. Holography shows the growth fringe concentration around the cylindric surface portion where the most rapid faces grow. A satisfactory interpretation of the experimental results is given on the basis of a new model which explains the growth of each single (hkl) face as the result of two processes of step generation on the surface and normal growth at the interphase of stepped and rough surface fraction around the [hkl] pole.