Cereal, root, tuber, and pith starches differ in their hygroscopicity or the amount of moisture retention.Little attention has been given to this characteristic and its possible correlation to other

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acid hydrolysis of starch has been used for over a century for the production of starch sirups and dextrose and as an analytical procedure for the determination of starch. This longcontinued use of the procedure would normally indicate wellestablished principles for the acid hydrolysis of starch. However, an examination of the literature on this subject indicates that the basic underlying conditions of hydrolysis are still not too well understood. The lack of clarity in published research may arise from two causes:The commercial hydrolysis of starch employs relatively high concentrations of starch and very low concentrations of acid in proportion to the starch.Published research on the reversion, polymerization, or condensation of dextrose by acid has employed high concentrations of acid in proportion to the dextrose so treated.The condensation polymerization of dextrose in more concentrated solutions under the influence of heat and small amounts of acid has received relatively little attention. This paper reports research on hydrolysis employing the usual variables of time, temperature, and acid concentration, more particularly the pH, but it is devoted chiefly to a study of the most neglected variable, carbohydrate concentration of the system, or the sugarwater ratio. This variable is shown to be more significant than any of the others on the final reducing sugar content. COMMERCIAL HYDROLYSIS OF STARCH

and must diffuse largely through the capillaries, a decided advantage may be gained through the use of vacuum drying. CONCLUSIONSIdeal conditions for thermal drying are: using diminished pressure to minimize time of diffusion of deep-seated moisture; using properly desiccated air to sweep the water vapor from the drying chamber; and heating the specimen at a temperature as close as possible to that at which the rate of thermal decomposition becomes appreciable. These conditions provide the maximum difference between the vapor pressure of the water in or on the substance and that of the air in the dryer. It is the magnitude of this difference, together with changes in moisture-vapor diffusion rates, that determines the rate of drying and the degree of drying possible by thermal methods.

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