Analysis 



375 



The limewater test for carbon dioxid. In crowded 

 and badly ventilated rooms carbon dioxid in unusual 

 amounts is in the air. It can be detected by the lime- 

 water test. 



Experiment 116. Pour an inch or two of limewater into 

 a glass. Does it turn milky ? Pump ordinary air through 

 it with a bicycle pump. Now blow air from your lungs 

 through a glass tube into some fresh limewater until it turns 

 milky. By this test you can always tell if carbon dioxid 

 (CO 2 ) is present. 



Carbon dioxid turns limewater milky as it combines 

 with the lime in the limewater to make tiny particles 

 (a precipitate) of limestone. If you pour seltzer water 



FIG. 189. The limewater test shows that there is carbon dioxid in the air. 



