30 EXPERIMENTAL PHYSIOLOGY 



left in the dish? What did the benzine do to the fat in the 

 flaxseed? Treat sugar or anything else that contains no fat 

 or oil in the same way. Is the result the same? (The 

 above method is another test for fat or oil.) 



XVII. MINERAL SALTS (OPTIONAL). 



Apparatus. Platinum foil or piece of sheet iron, forceps, piece 

 of meat or vegetable matter. 



Directions. Place the meat on the foil and hold the 

 foil in the flame with the forceps until all the black has 

 disappeared from the burning meat. The residue is min- 

 eral matter. Would this test be possible if this mineral 

 matter were combustible? What color is the residue? 

 (This is the test for determining the presence and amount 

 of mineral salts.) 



XVIII. WATER (OPTIONAL). 



Apparatus. Pieces of parsnip, potato, apple, lettuce leaves, flour, 

 meal, meat, test tube, balance sensitive to one gram. 



Directions. A. Heat one of the above substances in a 

 dry test tube. As the tube cools after having been taken 

 from the flame, examine the sides and note what you see 

 on them. In what form was the water before the tube was 

 cooled? 



B. Weigh a portion of each of the above substances, re- 

 cord the weights, and place the substances in a warm, dry 

 place for a few days. Then weigh again and record as be- 

 fore. Continue this until there is no further decrease in 



