EXERCISE 56 



Problem. What changes take place in a cracker when it is chewed in the mouth ? 



What to use. Soda crackers ; test tubes 1 ; iodin solution ; Fehling solution. 



What to do. Gather some saliva in a test tube ; test part of it for starch and part for grape sugar. 

 Test a piece of dry soda cracker for starch and for grape sugar. Chew a piece of soda cracker for two 

 minutes, being careful not to swallow any of it. Place a small amount of chewed cracker in each of two 

 test tubes. Test for starch and for grape sugar. 



Record. 2 



Questions. 1. What is the source of the sugar found ? 



2. How can you tell that it did not come from the saliva ? from the teeth ? 



1 You can increase the flow of saliva by chewing a piece of paraffin. 



2 Indicate presence by + and absence by 0. 



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