6(> VAPORIZATION. 



prevails over the attraction of the particles for one another, they 

 disperse in all directions, as long as they meet no obstacle, 

 and the body assumes the gaseous form. Berzelius adds the 

 reflection, that if, in that gaseous state, into which Cagnard 

 de la Tour reduced some volatile liquids, the pressure does 

 not correspond with the result of calculation, that difference 

 may depend on this : that, as the particles have not an oppor- 

 tunity to recede much, the two first forces continue always to 

 act, and oppose the tension of the gas, which does not establish 

 itself in all its power unless when the particles are so distant 

 from each other as to be out of the sphere of the influence of 

 these forces.* 



Gases. Permanent gases, such as atmospheric air, unques- 

 tionably owe their elastic state to the possession of latent heat. 

 But the theory of the similar constitution of gases and vapours, 

 although supported by strong analogies, was not generally 

 adopted by chemists, till it was experimentally confirmed by 

 Dr. Faraday, who liquefied several of the gases.f His method 

 was to generate the gas in one end of a strong glass tube, bent 



in the middle, as represented 

 in the figure, and hermeti- 

 cally sealed. The gas accu- 

 mulating in a confined space, comes to exert a prodi- 

 gious pressure, an effect of which is, that a portion of 

 the gas itself condenses into a liquid in the end of the 

 tube most remote from the materials, which is kept cool 

 with that view. Considerable danger is to be apprehended by 

 the operator in conducting such experiments, from the bursting 

 of the glass tubes, and the face ought always to be protected 

 by a wire-gauze mask from the effects of an explosion. The 

 names of the gases which were liquefied in this manner, are 

 sulphurous acid, cyanogen, chlorine, ammoniacal gas, sulphu- 

 retted hydrogen, carbonic acid, muriatic acid, and nitrous 

 oxide ; which required a degree of pressure varying, in the 

 different gases, from two atmospheres, in the first mentioned, 

 to fifty atmospheres, in the last mentioned gas, at the tem- 

 perature of 45. The liquefaction of several of these gases 



* Trait^ de Chimie, par J. J. Berzelius, 1. 1, p. 85. 

 t Philosophical Transactions, 1823, p. 189, 



