108 



REPORT — 1886. 



at initial pressure of about 760 mm.; and for h/drogen tlie mean of a num- 

 ber of experiments at 250° gave 099986, which is nearer to 1 than at 

 •ordinary temperatures ; as are also the above values for air (omitting 

 that for 0°) ; these being in fact distinguished from 1 by numbers of the 

 order of experimental error. 



Now air was found to deviate from Boyle's law in one direction and 

 hydrogen in the other direction when submitted to pressures of a few 

 atmospheres, and the efEect of the results here given is to show that both 

 these gases tend at higher temperatures to obey Boyle's law more nearly 

 than at lower. 



In ' Ann. Chim.' [4] 1873, xxix. pp. 246-285, Amagat considers the 

 rates of expansion with increasing temjjerature for SOo, COg, NHj, as 

 well as for hydrogen and air, and gives (p. 261) the following results for 



pv 

 p'v' 



where v is nearly 2v' for SO2 and CO2 ; at about 700 mm. 



At 



15° 



50° 

 100° 

 150° 

 200° 

 250° 



SO, 



10185 

 1-0110 

 1-0054 

 1-0032 

 1-0021 

 1-0016 



At 



CO, 



in which it is clearly seen how these gases also, as well as hydrogen and 

 atmospheric air, approach nearer to agreement with Boyle's law as 

 temperature rises. 



On page 279 Amagat gives a table of the coefficients of dilatation 



-— for different gases at different temperatures ; this table also shows how 



'O/t 



nearly they approach to each other and to Gay-Lussac's law in this 

 respect. 



The following selections will exhibit this : — 



The value of -— deduced from experiment. 



dt 



at 



The conclusion to be drawn from these results is that gases approach 

 more and more to conformity with Gay-Lussac's law (as well as with 

 Boyle's law) the higher the temperature, so far as the experiments have 

 been carried at ordinary pressures. 



Besults at High Pressure — Amagat. 



But the very thorough investigation of Amagat already mentioned 

 (p. 102) ' shows the relation of pv to p beyond the pressures treated of 

 hitherto in reference to Boyle's and Gay-Lussac's laws, curves being 



Annates de Chimie et de Physique, 1881 (6), xsii. pp. 353-398. 



