Separation of Cane Sugar from Water Ice

Abstract

Makers of ice-cream products occasionally find a water ice in which the cane sugar has cryst~lized, making the product hard, chalky in appearance, and unpalatable. The researches described in this paper may help those who have experienced such a difficulty, since the conditions governing the crystallization of sucrose from frozen solutions have been established with considerable exactness. In considering this problem, the solubility, temperature, and freezing-point relationships of cmae-sugar solutions of varying concentrations should be established if possible. Those temperatures incident to normal ice cream work are, of course, of primary interest. Upon the cooling of an unsaturated dilute solution to the proper point, ice separates from it. This separation concentrates the sugar in the unfrozen part, and as the temperature lowers this concentration increases. By plotting temperatures and concentrations incident to these temperatures, the freezing-point curve is obtained. Similarly, if a highly concentrated solution is cooled, its saturation point is reached, after which, under suitable conditions, sugar crystals are thrown out of solution. This process lessens the concentration of the sugar in the water, and increasingly lower temperatures are necessary to force out further crystals. These data, plotted in a manner similar to the freezing point data, yield the solubility curve. These curves approach each other, and at their point of coincidence is found a solution saturated to sugar and in equilibrium with ice. Under ideal conditions further abstraction of heat from this mass does not lower the temperature but brings about the separation of both sugar and ice until the mass has become solid, after which the temperature is of course lowered with further removal of heat.