PRELIMINARY EXPERIMENTS XV 



commonly found in plant and animal tissue, and it can be 

 formed only by life processes. Do acid and heat harden 

 or soften most substances ? Either of the above tests 

 reveals proteid, if present. Does cooking tend to soften 

 or toughen lean meat ? 



Another test for proteid is nitric acid, which turns pro- 

 teid (and hardly anything else) yellow. Proteid when 

 burned has a characteristic odor ; this will be noticed if lean 

 meat or cheese is charred in a spoon. The offensive odor 

 from decomposing proteid is also characteristic, whether it 

 comes from stale beans, meat, mushrooms, or other things 

 containing proteid. 



Test for Fats and Oils. Place a little tallow from a 

 candle on unglazed paper and warm. Hold the paper up 

 to the light and examine it. What effect has the fat had 

 on the paper ? Place a little starch, sugar, powdered chalk, 

 or white of egg on paper and repeat the experiment ; is 

 the effect the same ? Place some of the tallow in a spoon, 

 and heat. Compare the effect of heat on fat and proteid. 

 Water also makes paper semi-transparent, but it soon 

 evaporates : fat does not evaporate. 



Another test for fats is to mount a thin section of the 

 endosperm of castor-oil seed in water and examine with 

 high power. Small drops of oil will be quite abundant. 

 Treat the mount with alcanin (henna root in alcohol). 

 The drops of oil will stain red. This is a standard test 

 for fats and oils. 



To make or liberate Oxygen. If there is a chemistry 

 class in school, one of its members will doubtless be glad 

 to prepare some of the gas called oxygen, and furnish 

 several glass jars filled with it to the biology class. If 

 it is desired to make oxygen, the following method may 

 be employed : Provide a dry glass flask of three to four 



