94 
LABORATORY EXERCISES 
reading learn as much as you can of their economic importance. 
Note the characteristics of each, such as the size, the general color, 
the pecuhar markings, the food used, and the nature of the home. 
Note any adaptations which especially fit the animal for its mode 
of life. Plan a chart upon which to record your observations. 
APPENDIX 
I 
A TEST FOR CARBON DIOXIDE 
Add a little limewater to a test tube of the gas which is to be 
tested for the presence of CO 2 . If CO 2 is present, the limewater 
becomes milky in appearance. (A drop of limewater adhering 
to the end of a glass rod can be inserted in the tube. This is the 
most convenient method of applying the test.) The hmewater 
may be made by adding a piece of quicklime, about the size of an 
egg, to a quart of water. The liquid should be filtered before it is 
used. (See Waggoner, Fig. 123.) 
II 
A TEST FOR OXYGEN 
Lower a glowing Splinter into the gas which is to be tested for the 
presence of O. If it bursts quickly into a flame much free O is 
present. If it is extinguished, little or no free O is present. 
III 
FEHLING’S SOLUTION 
To prepare, make up the following solutions and keep in sepa¬ 
rate bottles: 
1. 35 gm. of copper sulphate dissolved in 500 cc. of H 2 O. 
2. 160 gm. of sodium hydroxide and 173 gm. of Rochelle salt 
dissolved in 500 cc. of H 2 O. 
When ready to use the solution, mix equal parts of the two. 
