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IX. On t/te Compressibility of Gases between One Atmosphere and Half an 



Atmosphere of Pressure. 



By LORD RAYLEIUH, O.M., F.R.S. 



Received January 17, Retul February '2, 1'JOo. 



THE present* is the third of a series <>f memoirs in which are detailed observations 

 upon the compressibility of the principal gases at pressures from one atmosphere 

 downwards. In the firstt of these the pressures dealt with were exceedingly low, 

 ranging from To millims. to O'Ol millim. of mercury, and the use of a sj>ecial and 

 extraordinarily delicate manometer allowed the verification of BOYLE'S law to be 

 pushed to about joKo f tt millimetre of mercury. 



In the second^ memoir the products of pressure and volume at constant temperature 

 (that of the room) were compared when the pressure was changed from 75 millims. to 

 150 millims. of mercury in the ratio of 2:1. The ratio of the products (denoted 

 by B) would be unity according to BOYLE'S law ; for the more condensable gases, 

 e.</., nitrous oxide, it exceeds unity. The following were the final mean values : 



* A Preliminary Notice containing many of the results now recorded in greater detail was published in 

 ' Hoy. Soc. Proc.,' February, 1904. 



t 'Phil. Trans.,' A 196, pp. 205-223, 1901 ; "Scientific Papers,' vol. 4, p. 511. 



J 'Phil. Trans.,' A 198, pp. 417-430, 1902. On p. 428, line 8 from bottom, read I+//IT instead 

 of 1 - WIT. 



The number for carbonic oxide was obtained subsequently to the publication of the memoir. It is 

 the mean of two sets of observations, giving severally 1-00003 and 1'OOOOS. The gas was prepared 

 from ferrocyanide of potassium (sec 'Koy. Soc. Proc.,' vol. 62, p. 204, 1897; 'Scientific Papers,' vol. 4, 

 p. 347). 



(380.) 6.4.05 



