316 



EBULLITION. 



Means similar to these have accordingly been applied, and succeeded, in 

 the hands of Faraday. By submitting gases in small quantities, in strong 

 glass tubes, to a severe pressure, produced by their own elasticity, and the 

 force with which they were generated by chemical action, heat was extracted 

 in considerable quantities, and was carried off by evaporation from the external 

 surface of the glass. In this way, nine gases were condensed into the liquid 

 form. 



Faraday attempted, without success, the condensation of various other gases 

 by the same means. Oxygen, azote, and hydrogen, have, it is said, been sub- 

 mitted to a pressure of eight hundred atmospheres without passing to the liquid 

 state.* 



It appears, therefore, that, in proportion as the powers of science are ad- 

 vanced, the exceptions to the general law of condensation become more and 

 more circumscribed ; and it is not, perhaps, overstepping the limits of justifia- 

 ble theory to assume, as a general law, that all bodies whatever, existing in 

 the gaseous form, may, by a sufficient abstraction of heat from them, be reduced 

 to the liquid state. 



The absorption of heat, in the process by which liquids are converted into 

 steam, will explain why a vessel containing a liquid, though constantly exposed 

 to the action of fire, can never, while it contains any liquid, receive such a 

 degree of heat as might destroy it. A tin-kettle containing water may be ex- 

 posed to the action of the most fierce furnace, and yet the tin, which is a very 

 fusible metal, will remain uninjured ; but if the kettle without containing water 

 were placed on a fire, it would be immediately destroyed. The heat which 

 the fire imparts to the kettle is immediately absorbed by the bubbles of water, 

 which are converted into steam at the bottom, and rendered latent in them. 

 These bubbles ascend through the water, and escape at the surface, continu- 

 ally carrying with them the heat conveyed from the fire through the bottom of 

 the kettle. So long as water is contained in the kettle, this absorption of heat 

 by the steam continues ; and it is impossible that the temperature of the kettle 

 can exceed the temperature of boiling water. But if any part of the kettle not 

 filled with water be exposed to the fire, there being then no means of dismis- 

 sing the heat which it receives from the fire, the metal will presently melt, and 

 the vessel be destroyed. 



The latent heat of steam may be used with great convenience for many do- 

 mestic purposes. In cookery, if steam raised from boiling water be allowed to 

 pass through meat or vegetables, it will be condensed upon their surfaces, im- 

 parting to them the heat latent in it before its condensation, and they will thus 

 be as effectually boiled as if they were immersed in boiling water. 



In dwelling-houses where pipes convey cold water to different parts of the 

 building, steam-pipes carried from the lower part will enable hot water to be 

 procured in every part of the house with great speed and facility. The cock 

 of a steam-pipe being immersed in a vessel containing cold water, the steam 

 which escapes from it will be condensed by the water, and will very speedily, 

 by imparting to it its latent heat, cause it to boil. Warm baths may thus be 

 prepared in a few minutes, the^water of which would require a long period to 

 boil. 



From all that has been explained in the present discourse, it will be apparent 

 that the solid, liquid, and gaseous states are not necessarily connected with 

 the essential properties of the bodies which assume these states respectively. 



* An opinion, which I consider to he erroneous, has hitherto prevailed, that gases and vapors 

 may be condensed by mere mechanical compression. I conceive that mechanical compression con- 

 tributes in no other way to the condensation of a gas or a vapor, than so far as it is the means of 

 raising the temperature of the gas compressed, and therefore facilitating the process by which it 

 may be deprived of heat. 



