of Ammonia, Sulphur dioxide, and Carbon dioxide. 377 



of the ratio of the molecular weights. Schweikert (Ann. 

 Phys. [iv.] xlviii. p. 593, 1915) reverted to the original 

 method of Kundt. At 19 o, and 1 atm. he gives 1*3006 as 

 the value of c p /c v . 



These results are not comparable, since they have been 

 calculated by different methods. In the following table, and 

 in the corresponding ones for the other two gases, the results 

 have therefore been re-calculated, using the value /c=l'403 

 for air and applying the corrections by Berthelot's equation. 

 Although the latter probably does not apply with extreme 

 exactness in the case of easily liquefiable gases (it is known 

 to apply exactly to carbon dioxide under the given conditions), 

 yet the deviations are so small as to be quite inappreciable 

 in the present case. The corrections are believed to be of a 

 much higher order of accuracy than those applied by the 

 previous experimenters themselves, who used methods open 

 to objection. It may be mentioned that much accurate 

 experimental work on the subject of the present communi- 

 cation has been completely vitiated, either by the assumption 

 of the laws of ideal gases or by. improper methods of 

 correction. Many of the values quoted in books of tables 

 are in error from this cause. 



Table III. 

 Ammonia. 1 atm. pressure. 



Author. 



Keutel . . . 



Scholer . . . 

 Schweikert. 



Cant and 

 Partington. 



cdvmi 



\/2 air 



20 11-370 

 20 11-837 



«NH,= 



9075 1 1-294 

 9-496 1-281 



1-279 



413-5 m. 331-9 m. 

 per sec. j per sec. 



14-5 10-320 



8-274 ; 1-285 



1-0174 

 10174 



c p/ c v j g. cal. g. cal. g. cal. 



1-317 j 2061 j 8*56 6-50 

 1-303 2-061 I S-86 680 



1-0218 1-307 



•079 ( 8-85 6-77 



1-0185 1-308! 2-065 ! 8- 



6-70 



KeutePs result for c p /c v appears to be a little too high ; 

 the rest are in satisfactory agreement. 



Sulphur dioxide. — The gas was taken from a siphon of 

 liquid, re-liquefied and fractionated as described. The 

 measurements were carried out at 1 atm. and 13°*2 C. The 

 following table gives the mean values for three experiments. 



