358 ORGANIC CHEMISTRY. 



% 



milky, as it passes through, from the fine starch grains 

 which it carries with it. These are allowed to settle, 

 and being collected and dried, are brought into com- 

 merce as potatoe starch. A cotton-cloth may be sub- 

 stituted for the seive in this experiment. 



903. STARCH FROM WHEAT. If wheat 



How is starch 



made from, flour is moistened with water, and exposed 

 to the air, it enters into a putrefaction which 

 destroys, in the course of a few days, the 

 other constituents, and leaves the starch un- 

 affected. The residue being then washed 

 and dried, the manufacture is completed. Io- 

 dine may be used as a test for starch, as described under 

 the head of iodides. Gums and woody fibre, although 

 of the same composition, are not similarly affected. 



904. CONVERSION OF STARCH INTO 



How is starch ... 1 



converted into SUGAR. Starch, like woody fibre, may be 

 converted into sugar through the agency 

 of sulphuric acid. A dilute acid containing only j\ of 

 its volume of oil of vitriol, is brought to the boiling 

 point, and the starch then added by degrees while the 

 boiling continues. A half hour or a little more suffices 

 for the conversion. An infusion of brewer's malt has 

 the same effect as the dilute acid. The sulphuric acid 

 is then to be removed, and the syrup concentrated as 

 before described. The sugar in this case also is grape, 

 and not cane sugar. Such sugar is manufactured largely 

 in Europe for adulterating cane sugar. In England 

 its manufacture is prohibited by law. 



905. CONVERSION OF STARCH INTO GUM. 



How is starch ,-,--. , , 



transformed By keeping the liquid near to the boiling 

 into gum? point, without actual boiling, the gum 



