54: HOW CROPS GROW. 



temperature rises to 375 F., the starch dissolves to a 

 nearly clear thin liquid. 



Amidulin also appears to be the first product of the 

 action of diastase (the ferment of sprouting seeds) on 

 starch and doubtless exists in malt. 



Soluble starch is colored blue by iodine and is thrown 

 down from its solution in water, or glycerine, by addition 

 of strong alcohol. It redissolves in water or weak alco- 

 hol. Its concentrated aqueous solutions gelatinize on 

 keeping and the jelly is no longer soluble in water. 

 Dilute solutions when evaporated leave a transparent 

 residue that is insoluble in water. 



On boiling together diluted sulphuric acid and starch 

 the latter shortly dissolves, and if as soon as solution has 

 taken place, the acid be neutralized with carbonate of 

 lime and removed by filtration, soluble starch remains 

 dissolved. (Schulze's Amidulin.) 



Amylodextrin. Nageli has described as Amylodextrin I and Amylo- 

 dextrin II, two substances that result from the action of moderately 

 strong acids on potato-starch at common temperatures. The starch 

 when soaked for many weeks in 12% hydrochloric acid remains nearly 

 unchanged in appearance, but the interior parts of the grains grad- 

 ually dissolve out, being changed into amylodextriii II, which closely 

 resembles and is probably identical with amidulin. 



The starch-grains that remain unchanged in outward appearance, if 

 tested with iodine solution from time to time, are at first colored blue, 

 but after some days they take on a violet tinge and after prolonged 

 action of the acid are made red and finally yellow by iodine. The grains, 

 which are now but empty shells, may be freed from acid by washing 

 with cold water, and then, if heated to boiling with pure water, they 

 readily dissolve to a clear solution (amylodextriii I), from which Xaj_ r i-li, 

 by freezing and by evaporation, obtained crystalline disks. These 

 bodies, when dry, have the same composition as cellulose, starch, and 

 amidulin. 



Dextrin (C 6 H 10 5 ) was formerly thought to occur 

 dissolved in the sap of all plants. According to Von 

 Bibra's investigations, the substance existing in bread- 

 grains, which earlier experimenters believed to be dex- 

 trin, is for the most part gum. Busse, who examined 

 various young cereal plants and seeds, and potato tubers, 

 for dextrin, found it only in old potatoes and young 



