20 PLANT BIOLOGY 



NOTE. In case a food which is being tested may possibly contain 

 a small amount of fat, the food should be pulverized, shaken in a 

 test tube with ether or benzine (to dissolve out the fat), and allowed 

 to stand for 24 hours. The clear liquid should then be poured upon 

 paper, and the ether or benzine allowed to evaporate. 



Caution. Never handle ether or benzine near a flame or hot stove, 

 since the vapor of these substances is very inflammable. 



27. To test foods for mineral matter. Laboratory Study 

 No. 12. Demonstration. 



Materials: Salt, corn starch, grape sugar, piece of boiled egg, 

 butter or fat, water. 



1. Place a piece of salt half the size of a pea on an old cook- 



ing spoon and heat over as hot a flame as possible. 

 Does the salt burn ? Does it disappear ? 



2. In the same manner try the effect of heat on the other 



food substances (starch, grape sugar, white of egg, fat, 

 water). Do any of these substances burn or disappear? 



3. From the preceding experiments state how you can deter- 



mine whether or not a food contains mineral matter. 



4. (Optional home work.) Test at home in the same manner as 



described in 1 above a match stick and a leaf. Do these 

 plant materials contain mineral matters ? How do you know ? 



28. To test foods for water. Laboratory Study No. 13. 

 Home work. 



1. Warm a little water on a spoon and place over it a dry, 

 cool, tumbler. What do you see on the inside of the 

 glass? How, then, can you tell whether or not water 

 is found in a given food? 



