204 POWDERED VEGETABLE DRUGS 



tissues on sieves. The starch grains quickly settle to the bottom of the 

 vat or other container, and the supernatant liquid containing the 

 tissue fragments and impurities is decanted off. The starch is again 

 washed and purified and finally dried. Before packing and marketing, 

 the lumps resulting from the drying may be coarsely broken, or the 

 hard masses may be reduced to a fine powder, in which the individual 

 granules become almost wholly separated. One of the methods for 

 purifying starch, is to agitate it in a dilute alkali, which dissolves 

 nitrogenous matter and other impurities. Unless this agent is very 

 carefully used and again quickly and completely removed, the starch 

 granules will also become partially dissolved and will show an alkaline 

 reaction. In the manufacture of starch from wheat, the gluten may 

 first be removed by a fermentation process, or the wheat flour is made 

 into a dough and the starch washed out of the gluten on a sieve. The 

 gluten is then used in making so-called gluten flour which is especially 

 recommended for diabetics. 



In the microscopical examination of starches, the following should 

 be looked for. 



1. Corrosion Effects. These may be due to the action of enzymes 

 or due to the prolonged or excessive action of the alkaline purifying 

 agent. If the corrosion effects are due to the action of bacteria (in 

 wheat starch obtained by the fermentation process) or mold, then 

 these organisms will be found in excess. 



2. Organic Impurities. These may be demonstrated by the 

 addition of iodine solution which stains them yellowish brown. 

 Starches with considerable organic matter usually also reveal bacteria 

 and other foreign matter, including dirt, sand, mold, and tissue ele- 

 ments, and such starches are brownish in color, and have more or 

 less odor. 



3. Admixtures and Adulterations. The more expensive starches 

 may be adulterated by adding a cheaper starch. Such practice is at 

 once recognized under the microscope. 



The following is the botonical source of the more important com- 

 mercial starches. 



1. Rye starch, Roggenstarke, G. From the grains of Secale 

 cereale L., Gramineae. The granules are very variable in size, the 

 largest measuring 60/i, the smallest 5 to 8/x. Some of the largest 

 granules with distinct fissured hili. 



2. Wheat starch, Weizenstarke, G. Amidon de ble, Fr. From 

 the grains of Triticum vulgare Vill., Gramineae. The granules are 

 similar to those of rye, excepting that the largest granules usually 

 do not exceed 50/n in diameter, and that they lack a distinct hilum. 



