Thermodynamic Properties of Air. 



307 



Table of the mean Coefficients of Expansion of Atmospheric 

 Air. (Values of 100000 . a p>e .) 



,_, Pressures 

 P atm. 









Temperatures 9. 









+100-0 



4-160 



-35-0 



-78-5 



-103-5 



-1300 



-1350 



-140-0 



-145-0 



S75 



376 

















15... 



379 



382 



... 







... 





420 



427 



20... 



383 



387 





401 



4ib 



427 





440 



450 



25... 



388 



392 





411 



422 



443 





463 



479 



30... 



392 



398 





420 



434 



462 



477 



492 



519* 



35... 



397 



403 





429 



448 



483 



506 



538 





40... 



402 



408 





438 



461 



508 



544 



632 





45... 



406 



414 





448 



474 



536 



594 







50... 



410 



419 



430 



457 



487 



569 



619 







55... 



414 



424 



436 



467 



500 



598 



623 







60... 



418 



429 



442 



476 



512 



610 



622 







65... 



421 



434 



448 



485 



525 



612 



621 







70... 



425 



438 



454 



494 



536 



612 









75... 



428 



442 



461 



503 



547 



610 









80... 



431 



446 



467 



512 



557 



607 









85... 



434 



449 



473 



520 



566 











90... 



437 



452 



479 



527 



572 











95... 



439 



455 



485 



532 



577 











100... 



441 



458 



489 



537 



579 











' 105.. 



443 



460 



493 



542 



580 











• 110... 



445 



462 



497 



545 



580 











i 115... 



447 



463 



499 



548 



579 











120... 



449 



465 



501 



550 



577 











125... 





466 



503 



551 



574 











130... 



... 



468 





551 



571 











* Corresponds to 29 atmos. 



This table, or, better still, the diagram on PI. L, shows very 

 clearly the kind of variation of the coefficient of expansion in 

 its dependence on pressure and temperature. For increasing- 

 pressures the coefficient increases, at every temperature, to a 

 maximum, and decreases subsequently. The higher the 

 temperature, the less pronounced is this maximum. 



The pressure corresponding to the maximum of expansion 

 diminishes with the temperature. From this it follows, that 

 the rate of increase of expansion is the higher, the less the 

 temperature. In the vicinity of the critical state (temp. = 

 — 141°, pressure 39 atm. nearly) the rate of increase of ex- 

 pansion is extremely great, the corresponding isothermal runs 

 here nearly vertically. The same holds good for temperatures 

 below the critical, at points where liquefaction occurs, for 

 instance at —145° and 30 atm. 



The isothermal lines of the coefficient of expansion form a 

 fan-shaped bundle converging nearly to one point, namely, 

 to the value 0*00367 at 1 atm. of pressure. If this were 



