108 Prof. Oersted on the Compression of Gases. 



experiments may be, and must be from their very nature, they 

 contribute to prove that the compressions produced by very 

 great powers, are regulated by the same laws as those pro- 

 duced by very low powers. But wishing to ascertain whether 

 the compression of every kind of gas was subject to the same 

 law, we selected such of the gases as are liable by the pressure 

 of a few atmospheres to be changed into a dewy liquid, par- 

 ticularly the sulphurous acid gas, which, (according to Fara- 

 day,) becomes such a liquid under the pressure of two atmo- 

 spheres. 



Two glass tubes of equal sizes, the one filled with well dried 

 sulphurous acid gas, the other with atmospheric air, were 

 placed in a small basin of mercury and put into an apparatus 

 by means of which these gases could be exposed to the proper 

 pressure. The result was, that both volumes were diminished 

 in a constantly equal ratio, till the moment when the sulphu- 

 rous acid gas began to liquefy. 



We add the following details of these experiments : 

 AAAA (fig. 4.) is a very strong glass cylinder, the same 

 which I use for the compression of water. This cylinder has 

 a brass lid ; on this is raised another cylinder BBBB, in which 

 a piston C is moveable up and down through the aperture 

 DD. EEEE are two equally graduated tubes, the lower ex- 

 tremities of which are fixed in a small iron basin FF. This 

 basin is fastened to a strip of glass GGGG, which serves at 

 the same time to keep the tubes in a perpendicular position. 

 The cylinder AAAA is filled with mercury up to HH. The 

 experiment is begun by the two tubes being filled with the 

 gases, put into the small basin, and fastened to the strip of 

 glass GGGG. The whole apparatus is then placed in the 

 cylinder AAAA, by which the basin is plunged into the mer- 

 cury below the line HH; the cylinder is then filled with 

 water, the pump-cylinder BBBB, put upon it, also filled with 

 water, and the piston made to press on the inclosed water. 

 The water communicates the pressure to the mercury, which 

 again transfers it to the gases in the tubes. Fig. 4. presents a 

 transverse section of the lower part of the apparatus. 



Experiments 



