Dr. Schroeder van der Kolk on Gases. 131 



Table of the Values of k for Air. 

 Pressure. 



Temperature. 



o 



-87 



4 



50 



100 



076. 



0-99862 

 1-00030 

 1-00055 

 1-00064 



1 metre. 



0-99749 

 1-00000 

 1-00040 

 1-00062 



2 metres. 



0-99300 

 0-99878 

 0-99986 

 1-00051 



The differences increase here regularly with the pressure and with 

 sinking temperature. 



From the values at —87°, 4°, and 100°, three formula? of 

 interpolation were calculated for the three pressures. There was 

 obtained, 



atO-76 *-{l<rai»-g™}K, 



i -, ™i.o 0-23366 1 rr 

 «tl- *= {1-00158 -j^^JK, 



at 2* ^{l-OMtf-^J^K, 



t is here the temperature on the Celsius scale. 



As a control, the value of k for 50° was calculated. There 

 w r as found — 



Pressure. From the formula. By direct observation. Difference. 

 m -76 1-00051 1-00055 4 



1 1-00038 1-00040 2 



2 0-99980 0-99986 6 



Hence between the above-mentioned limits of temperature the 

 formula? may be considered to be sufficiently accurate. 



By differentiating this formula, the values of -j are obtained. 



At 0'76 metre pressure, for instance, 



dk _ 0-11097K 

 dt "(131-4 + tf' 

 and thus at 4° C, 



die 



^= 0-0000060526 K. 



dt 



At 200° somewhat divergent results are obtained, perhaps 

 because the formula of hydrogen is too inaccurate at this tem- 

 perature. 



The value for carbonic acid was calculated in the same way. 



