26 THE NATURE AND NEEDS OF LIVING MATTER 



pears. Rinse out the acid with, water, and add a little ammo- 

 nia, and again note any change in color. 



Observations. 1. What change in color when the acid is 

 added ? Note. If a lemon-yellow color appears, it indicates 

 the presence of proteid. 



2. Is there a still further change in color when the ammonia 

 is added ? Note. A deep orange color now appearing verifies 

 the presence of proteid. 



Method b. Put some raw white of egg in a test tube, and 

 heat it. 



Observation. What happens as the white of egg is heated ? 

 What change in color? 



Note. Any substance thickening and becoming white in 

 color is said to coagulate, and indicates proteid in the form of 

 an albumin. 



Method c. Burn a piece of leather, or meat, or feather. 



Observation. Note the peculiar odor of burning feather or 

 leather. This shows the presence of a proteid. 



e. Mineral Matters (Optional) 



Method. Burn a piece of meat in a spoon or shovel until no further 

 change can be brought about by heat. 



Observation. What seems to be left in the spoon ? Describe it. 



f. Water (Optional) 



Method. Weigh the substance to be tested, as an ounce of meat. 

 Put it aside in a warm dry place, until it is thoroughly dry, and then 

 reweigh it. 



Observations. 1. What is the loss in weight of the meat ? 



2. What is the cause of most of the loss ? 



g. Summary 



Conclusions. 1. a. What do you conclude is a good test 

 for the presence of proteids in a substance ? b. Of fats and 

 oils ? c. Of starch ? d. Of grape sugar ? (e. Of mineral mat- 

 ter? / Of water?) 



2. Explain just what the test consists of in each case. 



