16 DEPARTMENT OF AGRICULTURE GEORGIA. [302] 



air, and will neither burn itself, nor support combustion, 

 immediately extinguishing a burning taper immersed in it. 



The gas may be generated by placing in a large jar 

 about two teaspoonfuls of muriatic acid, and adding to it 

 small pieces of limestone, marble, or a little carbonate of 

 soda, until all effervescence ceases. 



Effervescence shows that the gas is being liberated from 

 its combination with the lime or soda. If, after a few 

 minutes, a lighted taper is lowered into the jar, it will be 

 extinguished. 



The gas thus generated may be poured into another jar, 

 settling to the bottom and displacing the air. If the 

 lighted taper be now applied to the second jar, it will be 

 again extinguished. This experiment proves that the gas 

 is heavier than air, and that it will not support combustion. 

 The presence of lime in marl may be detected in this way. 



Carbolic acid gas is also formed when animal or vegeta- 

 ble matter is burned in the air 



The cause of the extinction of the flame when placed in 

 this gas is that there is no free oxygen present. That 

 which the gas contains has already as much carbon as it 

 can take up, and hence the carbon which forms a part of 

 the taper is left without any oxygen to combine with it to 

 support combustion. Animal life immersed in this gas is 

 immediately destroyed because of the exclusion of the ox- 

 ygen necessary to respiration, independently of the poison- 

 ous effects of the gas. This gas is often found in old wells, 

 and is then called choke-damp. Lives have been lost by 

 descending into these without first lowering a burning taper 

 to detect the presence of the gas. 



A quantity of lime water, made from freshly slaked lime, 

 thrown down the sides of the well will remove the gas by 

 its combination with the lime. 



Carbonic acid gas can, by pressure, be forced into liquids. 

 When the pressure is removed, effervescence is produced 

 by the escape of the gas. , 



