PLANT PRODUCTS 56 I 



Ammonia, NHs. The demonstration of ammonia in plant tissues is given in 

 the preceding chapter under Nessler's Reagent. 



Amygdalin. This nitrogenous glucoside is particularly abundant in bitter 

 almonds and in the bark, leaves, and flowers of Prunus padus. It may be extracted 

 by boiling water, and from a mixture of alcohol and water it crystallizes out in the 

 form of transparent orthorhombic crystals. From 80 per cent, alcohol it crystal- 

 lizes in the form of pearly scales. It is split up into prussic acid, oil of bitter almonds, 

 and sugar by an enzyme known as emulsin, which occurs within the plant along 

 with the amygdalin. 



Amylodextrine. This substance occurs in those starch-grains which take on 

 a reddish color with iodine, and it is formed by the action of diastase and acids from 

 the amylose of those starch-grains which are colored blue with iodine. By the 

 action of diastase on the starch of germinating seeds the amylose of the starch 

 is converted first into amylodextrine, and this in turn into dextrine and isomaltose. 

 The microchemical behavior of amylodextrine is given by Arthur Meyer as follows : 

 Water at 7oC. dissolves crystals of amylodextrine slowly, while at 100 the crystals 

 are dissolved at once. A solution of 10 Gm. of pure calcium nitrate in 14 Gm. 

 of water dissolves crystals under the cover-glass very slowly. After some hours, if 

 a solution of iodine is added, the calcium nitrate solution is colored brown, which 

 indicates that the crystals of amylodextrine have at least been partially dissolved. 

 A solution of 2 Gm. of purest potassium hydrate in 100 Gm. of water dissolves 

 small crystals within 2 hours, while the solution of larger crystals requires a longer 

 time. A solution of iodine, prepared as directed on page 548, colors the crystals 

 dark brown. A 25 per cent, solution of hydrochloric acid dissolves large and small 

 crystals immediately. When this solution is diluted with 4 parts of water, it 

 takes on a brownish-red color with the iodine solution. When I drop of malt 

 extract is added to 5 drops of a neutral solution of amylodextrine this becomes 

 inverted within 10 minutes, so that it no longer is colored by the iodine solution. 

 To prepare the malt extract treat i part of malt with 3 parts of water and filter 

 the solution. The solution of crystals of amylodextrine by the malt extract re- 

 quires several days. At a temperature of 4OC. saliva dissolves the amylodextrine 

 crystals within 48 hours. To prepare the saliva mix human saliva with a drop of 

 chloroform, filter, and preserve over a few drops of chloroform. 



Amyloid. This occurs as reserve material in the seeds of Tropceolum majus, 

 Impatiens balsamina, Paonia officinalis, and in many other plants. It is colored 

 blue by dilute solution of iodine, but with a concentrated solution it is colored 

 a brownish-orange. It is soluble in cuprammonia only after a day. Treated with a 

 30 per cent, solution of nitric acid it swells strongly, and finally dissolves. This is 

 different from the amyloid produced by the action of acids and certain chlorides 

 on cellulose. 



Amylose. Starch-grains which are colored blue by iodine that is, most 

 starch-grains are, according to Meyer, composed of crystals of two kinds of amy- 

 lose, named by Meyer a-amylose and /3-amylose. The a-amylose has been iso- 

 lated in crystalline form, but the /3-amylose has not been isolated, and its microchem- 

 ical behavior has only been determined by experiments with starch-grains. The 

 microchemical behavior of the a-amylose is as follows, the reagents being prepared 

 as directed under amylodextrine: Water at from 60 to iooC. does not soon 

 dissolve the crystals of this amylose. Treatment with the calcium nitrate solution 

 for 30 minutes does not appear to affect the crystals. The solution of iodine 

 does not color the crystals at first, but after a longer time it imparts a brownish 

 color. The solution of hydrochloric acid dissolves the crystals at once, and the 

 solution, diluted with four times its bulk of water, is colored deep blue with the 

 iodine reagent; but after the solution has stood for 12 hours it is colored brownish 



36 



