110 Prof. Oersted on the Compression of Gases. 



This table shows that the differences are very small, and 

 that sometimes one, and sometimes the other of the gases, suf- 

 fers a greater degree of condensation, up to a pressure of 2*3 

 atmospheres, where they become greater, and the sulphurous 

 acid gas shows continually a superior density. At a pressure 

 of 3*2689 the moisture begins to be visible, and the conden- 

 sation shows itself in a much more violent and decided manner. 

 Perhaps some small liquefaction takes place before it reaches 

 this point, where the gases come in contact with the glass and 

 the mercury, for the contact with a heterogeneous body seems 

 to favour the transition from one state of aggregation into an- 

 other, as I have shown in a former treatise on some experi- 

 ments of Winterl's*. 



In some experiments we found that the water had pene- 

 trated between the sides of the tubes and the mercury. This 

 inconvenience was subsequently obviated by our cementing the 

 extremity of the tube into a brass ring, which amalgamates with 

 the mercury, and prevents the water from penetratingf. 



We also compressed cyanogen in the same manner, and 

 found that the liquefaction of this gas begins when the air has 

 been compressed to 1-3*5 of its weight, at 23° of heat, and a 

 state of the barometer of 0*759 height of the mercury. 



It would be easy to multiply these experiments; but those 

 we have just communicated will, we trust, suffice to prove 

 that the compression of atmospheric air and of gases, is 

 in proportion to the compressing forces, however great the 

 latter may be, supposing that the gases remain in their aeri- 

 form condition, and that the caloric liberated by the com- 

 pression has been carried off. Thence it appears, that our 

 investigations have done no more than confirm the opinions of 

 the most distinguished men of science of our time with respect 

 to this subject; but as there still remained some who enter- 



* Vide Gehlen's Journal d. Phys. und Chem. 1806, vol. i. p. 276—89. 



f The means by which Professor Oersted thus succeeded in removing 

 this source of error, appears in some degree to confirm the results obtained 

 by Mr. Daniel!, in securing barometers from the deterioration ensuing from 

 the insinuation of air between the glass and the mercury at the lower end 

 of the tube. Mr. D. found, that welding a cylinder or a ring of platinum 

 to the extremity of the tube immersed in the mercury, effectually pre- 

 vented this evil j in the same manner as the insinuation of water between 

 glass and mercury was prevented by the Danish philosopher. Dr. Priestley 

 also found that the admission of air and of water into jars of gas confined 

 over mercury, was prevented by a little water poured around the jar upon 

 the mercury; and Mr. Faraday has ascertained that gases unconfinable 

 over mercury, may be preserved over water. The effect, in all these cases, 

 is attributable to the perfect contact ensuing from the juxta-position of 

 substances capable of acting chemically on each other. — E. W. B. 



tained 



