A water-jacketed viscosimeter for measuring the rate of liquefaction of starch pastes by diastase has been described;A macro volumetric modification of Hagedorn and Jensen's sugar method, applicable to following the course of amylase action has been developed;A potentiometric method of determining reducing values during amylase action has been developed;The temperature at which the substrate is prepared has been found to affect the rate of beta amylase action. Optimum temperatures for preparation of potato starch for amylase action is 70°, for tapioca 80°, for rice 80° or above, and for corn and wheat starches 85°90°;Methods of separating the flocculent material (precipitate A) and 60 percent alcohol insoluble residue (precipitate B) from beta amylase digestions have been described;The preparations were characterized as to further enzyme hydrolysis, phosphorus and fatty acid content, reducing action against ferricyanide and against copper, and recovery in the starch determination of Denny (14);The measured properties of precipitates A and B tend to show that precipitate A is a portion of precipitate B which is less soluble;Precipitates A and B from cereal and root starches show marked differences. These differences have not as yet been explained.