28 ELEMENTARY AGRICULTURE 



it up, and put it into a bottle. This powder is a com- 

 bination of lime and phosphoric acid. Now, if a little 

 water is poured over this powder and a small quantity 

 of sulphuric acid added, the lime will soon settle and 

 the clear liquid will be phosphoric acid. 



4. To prepare nitrogen, provide a glass bottle 

 with a large neck, a piece of wire, a bit of cotton, 

 a little alcohol, and a shallow dish containing lime 

 water to the depth of two inches. Twist one end of 

 the wire around a small piece of cotton, and then bend 

 it nearly double about three inches from the end bear- 

 ing the cotton. Dip the cotton in alcohol and light it. 

 Resting the wire loop on the bottom of the dish with 

 the torch standing upright, place the inverted empty 

 bottle over the torch so that the bottle rests on the 

 bottom of the dish and the ber.d in the wire. Soon 

 the flame dies out because the fire uses up the oxygen 

 in the bottle. The oxygen has united with the carbon 

 of the alcohol, forming carbon dioxide. Without 

 taking the mouth of the bottle from the water, remove 

 the torch, put one hand under the mouth of the bottle 

 to close it tight, invert the bottle quickly, and shake. 

 The lime water becomes milky, showing that the car- 

 bonic acid gas has been taken up by it. The colorless, 

 odorless, invisible gas now remaining in the bottle is 

 nitrogen. 



Plunge a lighted taper or splinter into the gas and 

 the flame is immediately extinguished, showing that 

 the gas is not air. 



