( ous form, iC'KrffOfi* ^. '^r.tense exn^^lon or grease of^uik. c^ 

 , rei'urr^iiu- 1:. ine liquid Orm, u^'Jergoes a corresponding c^'l ec""! i:;uf:ution 

 ' Jl bulk." A cabk m',r* of water transformed into steam at 212, charges in 

 5 magnitude t<* p',v:irjen hundred cubic inches, as already observed. The same 

 \ steam, ?ecT A verted into water by abstracting from it the he** consumed in its 

 ) vapor S;,an o2. will oe restored to its former bulk. :.nd will form one cubic inch 

 J 01 wn'.er at 212. Vapors raised from o'Ler h^iies would undergo a similar 

 ^ f^ar-ge, d:5ermp only in the desrree of diminution of bulk which they would 



< suffer ~espectiv iy. Tlie aiminiclied space into which the particles of a vapor 

 arr gradually condensed v.ucn it passes into the liquid state has rancid tins 



< pi oceaa ? Vo calloii condensation* 



/ No liquid nas been sub:r ;ttfi d to so minute an examination, with respect to 



< t'ie *$*'^ produced upon It Mr heat, as water ; and, with respect to other *li- 

 [uids, we are compelled, in the abso^e of experimental proof, to reason from 



inalogy The principle that the sum of iL? latent and sensible heats of vapor 

 is the *ame for all temperatures, may be extended, with a high degree of prob- 

 bbilit* , to the vapors of all liquids whatever; so that we nia^ sume this sum 

 to u . constant for each liquid, though differing in one liquid compared with 

 another. To maintain the vapor of any liquid in the aeriform state, it is there- 

 foie necessary that it should contain at least a certain quantity of heat, what- 

 ever ue its temperature ; and any diminution in this quantity cannot fail to 

 produce the condensation of a corresponding portion of the vapor. If the vapor 

 of a liquid, therefore, has received no heat after having passed from the liquid 

 to the vaporous form, it cannot lose any portion of the heat it contains without 

 a partial condensation ; but it is important to observe, that a vapor, whether of 

 water or any other liquid, may, after having attained the state of vapor, receive 

 an additional supply of heat to any extent, and may thus have its temperature 

 raised to any point whatever. Independently of the heat which it received in 

 the process of vaporization, all the heat which it has thus received in the state 

 of vapor it may lose, and yet remain in that state. Under such circumstances, 

 therefore, it must not be inferred that a reduction of temperature in vapor ne- 

 cessarily causes condensation. Condensation cannot commence until the vapor 

 loses all that heat which it received after taking the form of vapor ; but when it 

 has lost so much, then any further abstraction of heat must be attended by con- 

 densation. 



By the great change of volume which a vapor undergoes in condensation, it 

 becomes an efficient means of producing a vacuum, without the exertion of 

 mechanical force. Let a glass tube be provided, having at one extremity a 

 large bulb, the other extremity being open. Let a small quantity of liquid be 

 introduced into the bulb through the tube, and let a spirit lamp be placed under 

 the bulb, so as to cause the liquid to boil. The vapor of the liquid will first 

 mix with the air in the bulb and tube ; but, as its quantity increases, its elas- 

 ticity will cause k to issue through the tube, which it will at length raise to 

 its own temperature, so as to enable it to pass from the mouth of the tube in 

 the vaporous form, without being previously condensed. The stream of vapor 

 proceeding up the tube will, after a time, carry off with it the atmospheric air pre- 

 viously contained in the bulb and tube ; and at length the space below the mouth 

 of the tube will be completely filled with pure vapor. Let the tube be now 

 inverted, and its open end plunged in a vessel of water or other liquid, the 

 bulb being presented upward. The space within the tube and bulb containing 



* In general, whenever the dimensions of a body are diminished, without any diminution of its 

 quantity of matter, it is said to be condensed, and the process may without impropriety be called 

 condensation ; but this more general application of the term cannot cause any confusion, since its 

 meaning is always easily understood from the context. 



