C 8 7 ] 



precipitated by that acid in the form of carbo- 

 nate of lime, or limeftone. If the water be fatu- 

 rated with carbonic acid, it will diffolve carbonate 

 of lime in confiderable quantity ; and if this folu- 

 tion be let fall drop by drop on any fubftance, or 

 the carbonic acid efcapes, the carbonate of lime 

 will be depofited in the incrufted fubftance with 

 calcareous earth, and the fubftance is faid to be 

 petrified. 



HYDROGEN^ GAS, 



OR 



INFLAMMABLE AIR, 



Inflammable Gas> or Phlogiston of Kirwan. 



Hydrogen, which is the bafe of water, com- 

 bined with caloric, forms hydrogen gas, or inflam- 

 mable air, difcovered by Mr. Cavendifh in 1767. 

 It is the lighteft of elaftic fluids, being twelve 

 times lighter than common air; hence employed 

 in air-balloons. It inflames by contact of an ig- 

 nited body, but will burn only in contacl with com- 

 mon, or oxygen, air. It is lefs noxious than the 

 carbonic acid: fuffers no diminution on mixture 

 with nitrous air. It is produced during the dif- 

 folution of animal and vegetable bodies ; hence it 



(k) Hydrogenium (v^oysviov, from v$wp, water, and ywp&jt to 

 become, or ytwctw, to produce) hydrogen, one of the princi- 

 ples of water. The bafe of that elaftic fluid, which was for- 

 merly called inflammable air. 



