1 24 CARBOHYDRATES. 



III. AMYLOSES. 



STARCH GROUP. 



Starch. Occurs in nature as granules consisting of granulose 

 in a skeleton of cellulose. 



1. To a tube two-thirds full of cold water add a couple of 



pinches of starch, shake briskly, it does not dissolve. 

 Boil, a dull solution results. If enough starch is 

 present it forms a gelatinous mass on cooling. Starch 

 mucilage. 



2. To some of the solution add iodine solution = Blue colour. 



Iodide of starch. Heat the blue solution, the colour 

 disappears to return on cooling. 



3. To a little (1) diluted add a few drops of NaOH. Iodine 



does not give a blue colour in an alkaline reaction. 



Transformations of Starch. Take as much powdered starch 

 as can be heaped on a penny, place it in a beaker and rub 

 it into a cream with a little cold water. Add this gradually 

 to 50 cc water which is boiling briskly in a beaker and stir 

 thoroughly until all the starch is swollen, which will take from 

 five to six minutes. Thick starch mucilage (A). 



Place a little of this in a tube. Dilute it and test 

 with iodine and with Fehling. No reduction absence 

 of sugar. 



As soon as the temperature of the original starch mucilage 

 has fallen to 40 C. it thickens markedly, then add to it 5 cc of 

 pancreatic extract, or of your own saliva 1 , stir continually. 

 In a few minutes the mucilage will turn quite fluid through 

 the action of the ferment. 



1 Obtain your own saliva as follows : Hold a tube against the lower lip to catch 

 the saliva. Open your mouth slightly and breathe the vapour of acetic acid from 

 the reagent bottle. At least 10 cc should be collected. 



