LABORATORY EXERCISES 401 



(6) Put a few drops of 1% copper sulfate solution in test tube, and 

 add solution of grape sugar (dextrose) ; then add a few drops of strong 

 caustic potash solution and boil ; a rust-red precipitate is formed in bot- 

 tom of tube (cuprous hydrate or oxide). 



If cane sugar is used, the above result will not follow unless the sugar 

 solution is first treated with a few drops of 25% solution of sulfuric acid 

 and then boiled ; after this treatment, proceed as in case of dextrose and 

 same result follows. Unmodified cane sugar does not contain dextrose. 



Test starch or white of egg in the same way and show that the reaction is 

 negative. 



Page 32. Put a small bit of fat meat (of size of pea is sufficient) in 

 test tube and then pour in a little 1% solution of osmic acid. The fat 

 turns black. 



Place a few drops of olive oil in a test tube with a little water and shake 

 vigorously. The oil forms a milky white emulsion. Examine a drop of 

 milk with a microscope, and note the fat globules forming an emulsion. 

 Put a small bit of fat meat on a perfectly dean slide, pour on a little ether 

 and allow to evaporate ; the ether dissolves the fat and on evaporation 

 leaves a scum on the glass. 



Tests of same sort with proteids or carbohydrates give negative 

 results. 



Page 34. Boil tough, gristly pieces of meat and cut bones in a little 

 water. A jelly will form as the solution cools, which illustrates the 

 nature of gelatin. 



CHAPTER III 



Page 37. Since the character of the teeth is an indication of what an 

 animal eats, it will be instructive to show different sorts of skulls with 

 teeth in position ; e.g. the human teeth indicate omnivorous diet ; the rab- 

 bit teeth indicate herbivorous diet ; the cat or dog teeth indicate carnivo- 

 rous diet. 



Page 40. Boil an egg for ten minutes and remove the shell. Cut in 

 halves to show the coagulated albumen and the yolk. Put some of the 

 coagulated white in water and heat to prove that it will not dissolve. 

 The white of raw egg coagulates in strong acid the same as in boiling 

 water. 



Page 42. The proteid value of foods will be made more vivid if a 

 considerable list of foods is on hand in quantities which can be used in 

 connection with the table. 



