FOOD EXPERIMENTS 85 



add 1 in. of water and a /4 in. of sodic hydrate solution. Then 

 add carefully 1 to 2 drops of copper sulphate solution. Heat 

 the upper half of mixture in flarne of Bunsen burner or alcohol 

 lamp, by holding tube at an angle of 45. Bring to a boil and 

 note the characteristic change due to the presence of sugar 

 (Trammer's Test). Test similarly 1 various vegetables, fruits 

 and milk. 



6) Test for proteid (Xantho-proteic "reaction) : Put in a test 

 tube l / 2 in. of solution of white of egg. 2 Add l /z in. of con- 

 centrated nitric acid. Heat gently to boiling and continue until 

 a yellow color develops. Let cool and add strong ammonia 

 until the solution is alkaline (turns red litmus paper blue). 

 Note the change to orange color, which is characteristic of 

 proteid reaction. 



Test similarly 3 wheat flour, various meals, vegetables, fruits, 

 milk and meats. 



7) Determine the proportion of water in meat, fat, milk, 

 vegetables and fruits, by weighing fresh, chopping fine, drying 

 quickly where they will be warm but not heated and re- 

 weighing. 4 



8, a) Structure of milk: Examine a drop under microscope 

 and sketch the oil globules. 



b) Test for fat: Dry with moderate heat a tablespoonful of 

 milk in a shallow tin vessel. When perfectly dry, pour upon 

 it a small amount of gasolene or ether, being sure to have 

 no flame of any kind in the room. Put some of the solution 

 upon a glass or piece of paper and allow to evaporate. Note 

 residue. 



c) Precipitation of casein: Place warmed milk in a small 

 glass. Add drop by drop a dilute solution of acetic acid 

 (vinegar) and stir constantly until a precipitation of casein to- 

 gether with fat is formed. Let settle or filter. Dry precipitate 



1 In case of solid vegetables and fruits, crush, shake in a little 

 water and use the clear solution. 



a Cut white of raw egg repeatedly with scissors. Shake in a 

 bottle with 20 parts of water; let settle and filter. Use clear 

 solution. 



8 In case of solids, put % in. of water into a test tube and add 

 the solids to be tested. Proceed as with white of egg solution. 



4 Ordinarily drying takes from 24 to 48 hours even under the 

 most favorable circumstances. 



