244 Domestic Science 



EXPERIMENT 103. Place a layer of moistened saw- 

 dust at the bottom of a gas-jar. On this drop some 

 French or haricot beans, or other large seeds. Cork 

 up the mouth of the flask firmly and store it in a warm 

 place in the dark for some days. Examine the jar 

 from time to time, and when the seeds have germinated, 

 allow them to grow for two or three days. At the end 

 of that time, uncork the flask, and test the contents by 

 inserting (a) a drop of lime-water on the end of a glass 

 rod ; (6) a lighted taper. The air of the jar will afford 

 evidence of the presence of a considerable proportion of 

 carbon dioxide when tested in this way. 



The decay of all forms of plant life is of the nature 

 of slow combustion and is attended by the formation of 

 much carbon dioxide. 



EXPERIMENT 104. Fit up two large jars as indicated 

 in Fig. 74. Half fill one with moist decaying vegetable 

 matter, such as dead leaves. Fit the cork and tubes 

 to the jar and allow it to remain undisturbed in a warm 

 place for about a day. At the end of that time con- 

 nect the outlet tube with the inlet tube of the second 

 jar, having previously poured a quantity of clear lime- 

 water into the latter vessel. Attach an aspirator or 

 pump to the outlet of the second jar and cause a gentle 

 stream of air to pass through the apparatus for a short 

 time. The production of turbidity in the lime-water 

 in a much shorter time than was the case in Experiment 

 93 affords evidence that the air in the jar containing 

 the decaying matter is considerably richer than ordinary 

 air in carbon dioxide. 



166. The water- weed in Experiment 102 was said to 

 obtain a supply of carbon dioxide from the water in 

 the flask. In addition to carbon dioxide, the other con- 

 stituents of the air also dissolve in water to some extent. 



