228 THE CARBOHYDRATES. 



formed as an intermediate step in the conversion of starch into sugar 

 by dilute acids or diastatic enzymes. Soluble starch may be precipitated 

 from very dilute solutions by baryta-water. 1 



Starch granules swell up and form a pasty mass in caustic potash or 

 soda. This mass gives neither MOORE'S nor TROMMER'S test. Starch 

 paste does not ferment with yeast. The most characteristic test for starch 

 is the blue coloration produced by iodine in the presence of hydriodic 

 acid or alkali iodides. 2 This blue coloration disappears on the addition of 

 alcohol or alkalies, and also on warming, but reappears again on cooling. 



On boiling with dilute acids starch is converted into glucose. In 

 the conversion by means of diastatic enzymes we have, as a rule, besides 

 dextrin, maltose, and isomaltose, only very little glucose. We are 

 considerably in the dark as to the kind and number of intermediate 

 products produced in this process (see Dextrins) . 



Starch may be detected by means of the microscope and by the 

 iodine reaction. Starch is quantitatively estimated, according to SACHSSE'S 

 method, 3 by converting it into glucose by hydrochloric acid and then 

 determining the glucose by the ordinary methods. 



Inulin (C6HioO5)x+H2O, occurs in the underground parts of many 

 Composite, especially in the roots of the Inula helenium, the tubers 

 of the Dahlia, the varieties of Helianthus, etc. It is ordinarily obtained 

 from the tubers of the Dahlia. 



[Inulin forms a white powder similar to starch, consisting of spheroid 

 crystals which are readily soluble in warm water without forming a paste. 

 It separates slowly on cooling, but more rapidly on freezing. Its solu- 

 tions are levogyrate and are precipitated by alcohol, and are colored 

 only yellow with iodine. Inulin is converted into the levogyrate mono- 

 saccharide d-fructose on boiling with dilute sulphuric acid. Diastatic 

 enzymes of higher animals have no, or only a very slight, action on inulin. 4 



According to DEAN 5 inulin occurs in combination with other substances, 

 levulins, which are more soluble and have less rotation. He suggests that we 

 limit the name inulin to that carbohydrate (or mixture of carbohydrates), which 

 is readily precipitable by 60 per cent alcohol and shows a specific rotation of 

 (a) D =-3Sto40. 



Lichenin (MOSS-STARCH) occurs in many lichens, especially in Iceland moss. 

 It is not soluble in cold water, but swells up into a jelly. It is soluble in hot 

 water, forming a jelly on allowing the concentrated solution to cool. It is colored 

 yellow by iodine and yields glucose on boiling with dilute acids. Lichenin is 

 not changed by diastatic enzymes such as ptyalin or amylopsin (NILSON 6 ). 



1 In regard to the compounds of soluble starch and dextrins with barium hydroxide, 

 see Biilow, Pflviger's Arch., 62. 



2 See Mylius, Ber. d. deutsch. chem. Gesellsch., 20, and Zeitsch. f. physiol. Chem., 11. 



3 Tollens' Handb., 2. Aufl., 1, 187. 



4 Tollens' Handbuch, 208. 



5 Amer. Chem. Journ., 32. 



6 Upsala Lakaref. Forh., 28. 



