The starch grains are spherical, or nearly so, have a very indistinct nucleus, react only feebly with polarized light, rapidly lose the blue coloration imparted by iodine, and show only a slight tendency to unite in the form of compound grains; three or four is usually the maximum number so united. The size of the grains of cocoa starch is usually stated to be 0.003-0.010 mm. The following measurements were made in this laboratory:

Measurements of starch grains from a sample of unprepared cocoa beans.

Measurements of starch grains from Walter Baker & Co's. "cracked cocoa."

For the preparation of the sample for microscopical examination, a convenient portion is washed with ether by decantation in a small test tube; when the ether has evaporated from the residue, a portion is triturated in a small mortar with a small quantity of solution of chlorinated soda until nearly or just decolorized; the mixture is then washed into a large test tube, or conical glass, diluted with much water, and set aside to settle. The sediment thus obtained is removed with a pipette for the microscopical examination. If both color and form are found necessary for the identification of any structures, the reserved portion of unbleached and fat-free material is used for this purpose.

A knowledge of the structures of the spices used for flavoring cocoa preparations, sufficiently accurate to enable one to readily distinguish them from substances added as adulterants, is very important; to identify the individual spices when several have been used in the same preparation is a very difficult and generally a highly unimportant problem. The ordinary flavoring materials are vanilla and cinnamon; cloves, nutmeg, mace, cardamom, Peruvian balsam, and artificial vanillin are also reported as flavoring materials.

Starch, flour, and husks are the more ordinary adulterants to be detected with the microscope; Moeller1 reports the materials most commonly used to be wheat and potato starches, next rice and arrowroot, and finally wheat, acorn, and rye flours, ground peanuts, and in malted preparations raw malt as a substitute for malt extract; to these Mace2 adds almond cake and sawdust. As the collecting of valueless waste products and the converting them into suitable materials for the adulteration of commodities of value has become a well-established industry, every investigator must be prepared to find many new substances used for this purpose, and must not be disappointed if he finds none of those that have recently been reported. To know what to expect to find, he should consider the current prices, abundance, and suitability of available materials, as well as the results of previous investigations.