THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



AUGUST 1886. 



XL The Law of Attraction amongst the Molecules of a Gas. 

 By William Sutherland, M.A., B.Sc* 



MANY hypotheses have been advanced as to- the law of 

 force prevailing among the molecules of a gas, chiefly 

 with a view to furnishing an explanation of part of the 

 departures from Boyle's and Charles's laws ; but, as they have 

 not started from a clear experimental basis, they have led to 

 no general result of any value. The clearest evidence which 

 has yet been given of the actual existence of attractive forces 

 amongst the molecules of gases was supplied by the difficult 

 experiments conducted by Thomson and Joule between the 

 years 1852 and 1862, and described in their papers in the 

 ' Philosophical Transactions ' on the " Thermal Effects of Fluids 

 in Motion."" But of the two striking general conclusions 

 which they were able to draw from their experimental results, 

 no use has been made except that which they themselves made 

 in employing them to obtain an accurate expression of the 

 relations of volume, pressure, and temperature in the case of 

 air. The object of the present paper is to show that Thomson 

 and Joule's experiments prove that the molecules- of a gas 

 attract one another with a force inversely proportional to the 

 fourth power of the distance between them, and directly 

 proportional to the product of their masses. It is hoped, too, 

 that the attention of physicists will be recalled to the power 

 of Joule's method in attacking the great problem of molecular 

 attractions in solids and liquids. 



* Communicated by the Author. 

 Phil. Mar,. S. 5. Vol. 22. No. 135. Aug. 1886. G 



