58 PLANT GROWTH AND NUTRITION 



b. Test with Benedict's Solution 



Materials. — The same as above, but substitute for Fehling's 

 solution Benedict's second solution. 1 



Method. — Place the material to be tested in a test tube with 

 an equal amount of Benedict's solution. Heat to boiling. Con- 

 tinue boiling for two minutes. 



Observations. ; — Are there any changes in color? 



NOTE. — If grape sugar is present, a precipitate will be formed having a red, yel- 

 low, or green color, depending upon the amount of sugar present. 



Conclusion. — 1. Is grape sugar present in the material tested? 



2. Test apples, grapes, bananas, pears, or any other fruit to see 

 whether grape sugar is present. 



3. Make a table showing the amount of grape sugar present in 

 various foods. 



Problem 28 : To test for fats and oils. 



Materials. — Nuts or animal fat, white paper. 



Method. — Rub the nut or material to be tested on a piece of 

 paper, and hold to the light, or put material to be tested on a piece 

 of white paper in an oven for a few minutes. 



Observations. — What happens to the paper? 



Conclusion. — How would you know the presence of oil in a 

 substance ? 



NOTE. — Ether and benzine extract oils from substances, and on evaporation 

 leave the oil on the container. 



Test beans in this manner and write out in problem form for extra credit. 



Problem 29 : To test for proteins or nitrogenous foods. 

 Materials. — Raw and hard-boiled white of egg, hair, nitric 

 acid, ammonia, test tubes. 



1 Benedict's second solution. — Copper sulphate 17.3 g. 



Sodium citrate 173.0 g. 



Sodium carbonate (anhydrous) . . . 100.0 g. 

 Make up to 1 liter with distilled water. 



With the aid of heat dissolve the sodium salts in about 600 c.c. of water. Pour 



through filter paper into a glass graduate and make up to 850 c.c. with distilled water. 



Dissolve the copper sulphate in about 100 c.c. of water, and make up to 150 c.c. 



with distilled water. Pour the carbonate citrate solution into a large beaker and 



add the copper sulphate solution slowly with constant stirring. 



After Hawke's Biochemistry. 



