56 HOW CROPS GROW. 



EXP. 28. Cautiously heat a spoonful of powdered starch in a porce 

 lain dish, with constant stirring so that it may not burn, for the space 

 of five minutes; it acquires a yellow, and later, a brown color. Now 

 add thrice its bulk of water, and heat nearly to boiling. Observe that 

 a slimy solution is formed. Pour it upon a filter; the liquid that runs 

 through contains dextrin. To a portion add twice its bulk of alcohol ; 

 dextrin is precipitated. To another portion, add solution of iodine ; 

 this shows the presence of dissolved but unaltered starch. To a 

 third portion of the filtrate add one drop of strong sulphuric acid and 

 boil a few minutes. Test with iodine, which, as soon as all starch is 

 transformed, will give a red instead of a blue color. 



Not only heat but likewise acids and ferments produce 

 dextrins from starch and, according to some authors, 

 from cellulose. In the sprouting of seeds, dextrin is 

 abundantly formed from starch and hence is an ingre- 

 dient of malb liquors. 



The agencies that convert starch into the dextrins easily 

 transform the dextrins into sugars (maltose or dextrose), 

 as will be presently noticed. 



The chemical composition of dry dextrin is identical 

 with that of dry cellulose, starch, and amidulin. 



Inulin, C 36 H 62 36 , closely resembles starch in many 

 points, and appears to replace that body in the roots of 

 the American artichoke,* elecampane, dahlia, dandelion, 

 chicory, and other plants of the same natural family 

 (composite). It may be obtained in the form of minute 

 white grains, which dissolve easily in hot water, and sep- 

 arate again as the water cools. According to Bouchar.dut, 

 the juice of the dahlia tuber, expressed in winter, becomes 

 a semi-solid white mass after reposing some hours, from 

 the separation of 8 per cent of inulin. 



Inulin, when pure, gives no coloration with iodine. It 

 may be recognized in plants, where it occurs as a solu- 

 tion, usually of the consistence of a thin oil, by soaking 

 a slice of the plant in strong alcohol. Inulin is insolu- 

 ble in this liquid, and under its influence shortly separ- 



* Helianthus tuberosiis, commonly known as Jerusalem artichoke, and 

 cultivated in Europe under the name topmamhour, is a native of the 

 Northern Mississippi States. 



