GASEOUS BODIES. 75 



It may be observed that while oxygen is in many in- 

 stances so beneficial to the lungs and revivifying, and in 

 combination is so injurious to the stomach and system ; 

 carbonic acid gas produces death, if attempted to be 

 breathed, while some of its compounds, as the carbon- 

 ates of potash, of magnesia, of ammonia, &c., are occa- 

 sionally most beneficial to the system. 



This gas * very strongly resists putrefaction, so that 

 meat has been kept in it for years without becoming 

 even tainted. 



Water is a compound of Oxygen and Hydrogen, con- 

 sisting of about 85 parts by weight of the former, and 

 15 of the latter, or of about one part by measure of the 

 former, and two parts of the latter. 



Hydrogen, like oxygen, takes its name from a Greek 

 word, and implies a generator of water ; it is only known 

 in a gaseous form, or in combination with other bodies. 

 Hydrogen, when in an aerial state, or hydrogen gas, is 

 the lightest of all known substances, being fourteen times 

 lighter than common air. From its extreme buoyancy, 

 aeronauts formerly used it to fill their balloons ; but from 

 the facility with which coal-gas is obtained, the latter is 

 now generally used, though not so buoyant. 



Hydrogen gas will not support life, as animals, when 

 obliged to breathe in it, die almost instantaneously ; nei- 

 ther will it support flame, as a burning body is instantly 

 extinguished when immersed in it, but when in contact 



in a state of gas. Ammoniacal gas is of a very volatile natare, has an 

 extremely pungent smell, and will neither support life nor flame. 

 When combined with water, for which it has a great affinity, it forms 

 liquid ammonia, and in this state it is used in our manufactories, and 

 in medicine. Animal and vegetable substances in a state of putre- 

 faction give out this gas ; it may be procured by the distillation of 

 bones, and also from the gas-works. Ammonia forms various com- 

 binations ; it combines with muriatic acid gas, and forms muriate of 

 ammonia or sal ammoniac, a substance much employed by dyers, 

 braziers, and others, as well as in medicine. It was from this sub- 

 stance sal ammoniac being dug out of the earth near the temple of 

 Jupiter Ammon, that it received its name. 



* Charcoal also, which has carbon for its base, is noted for its 

 antiseptive properties. For this reason vessels are charred which are 

 intended to contain water in sea voyages. Meat, also, slightly tainted, 

 .ay, by the application of charcoal, be almost instantly made sweet, 

 E 2 



