74 PHYSIOLOGICAL AND PATHOLOGICAL CHEMISTRY. 



a small quantity of material resembling cellulose, which comes 

 from the starch, evaporate on the water-bath o about 100 cc., 

 filter again, and evaporate to about 25 cc Pour this sirup 

 while still hot into a flask containing 100 cc. cf 90 per cent, 

 alcohol heated to boiling on a water-bath, heat a little longer, 

 shake thoroughly, and let stand till next day. The precipi- 

 tate consists of dextrin with some maltose; the alcoholic solu- 

 tion contains principally maltose with a little dextrin and 

 traces of glucose. A perfect separation is not attainable by 

 a single precipitation with alcohol, and also requires a larger 

 amount of material. On the next day pour off the alcoholic 

 solution and wash once with alcohol the glutinous precipi- 

 tate sticking to the flask. 



(a) Pour on the residue in the flask about 50 cc. of water, 

 heat to boiling (with constant shaking so that the precipitate 

 may not be burned or heated too highly), and boil the 

 solution until the odor of alcohol has completely disap- 

 peared. Let cool, dilute to 100 cc., and filter through a dry 

 filter. 



A small portion of this solution turns blue-violet on the 

 addition of a very small quantity of iodine solution, and red 

 with a larger quantity. Sometimes these colors with iodine 

 are not given because achroodextrin has been formed. The 

 solution gives the reactions for sugar very markedly. 



Thirty cubic centimeters of the solution obtained are 

 diluted to 150 cc. Add 10 cc. of hydrochloric acid to 100 cc. 

 of the solution and mark this solution A. The remainder, 

 50 cc., is used to determine the rotation. It amounts to, 

 say, 6.8 per cent, calculated as glucose. 



The solution A is then heated to boiling and kept boiling 

 gently for twenty minutes. Let cool, fill up to the former 

 volume (100 cc.), and again determine the rotation (neutral- 

 ization of the solution may be omitted, if we determine the 

 rotation rapidly and clean out the observation-tube at once; 



