MANUAL OF GENEEAL AGEICULTUEE. 41 



of caustic potash (potassium hydroxid.) Warm but do 

 not cook the egg. Add a few drops of a 10% solution 

 of blue stone (copper sulfate) and let stand until next 

 laboratory period. At first a greenish blue color appears 

 and in ten or fifteen minutes a beautiful violet color proves 

 the presence of proteids. 



(c) Fats and Oils. Grind a tablespoonful of oats, 

 barley, or corn. If the grinding cannot be conveniently 

 done use bran, flaxseed, or any ground feed. Place in a 

 bottle and pour over it 15 c.c. of ether$. Stopper, shake 

 well at intervals for half an hour or let stand until the 

 next laboratory period. Filter the liquid into a clean 

 evaporating dish and allow the ether to evaporate in the 

 open air. The residue is plant fat and oil. 



38. OCCURRENCE AND EXTRACTION OF STARCH. 



Materials: Compound microscope, piece of potato, 

 grater, beaker, evaporating dish, test tube holder, glass 

 tube 8 in. long, lime water, ring-stand, one-hole rubber 

 stopper for test tube, cheesecloth. 



(a) Examine a thin section of potato under the 

 microscope. Make a careful drawing of the structure 

 of the cells and granules within. Cover the section with 

 a cover glass and introduce a minute trace of iodine 

 solution at the edge of the cover glass. Make a shaded 

 or colored (blue pencil) drawing of the object. 



(b) Clean and peel one end of a potato. Rub it on 

 a grater and collect the gratings in a beaker of cold 

 water. Strain through a cheesecloth and allow the cloudy 

 liquid to stand until the starch settles. Pour off some of 

 the liquid and evaporate some of it to dryness in an 

 evaporating dish. Describe the residue. 



Heat a small portion of starch in a test tube. What 

 does this show starch to contain? Take another test tube 

 and fill it one-third full of lime water. Insert into the 

 test tube containing the starch a one-hole rubber stopper. 

 Bend a glass tube 8 inches long into a right angle, and 



JDo not place ether near a flame. 



