122 



Prof. J. Prestwich. 



Tempera- 

 ture. 



Pressure 

 of 



I* 1*6 S 9111*0 



in atniO" 



SpilGPGS. 



Tempera- 

 ture. 



PliflQCl IT»A 



X ICO&LU C 



of 



XIit/XCU.1 V. 



Ill dl/iilU 



b Ulit/X CO* 



F. 



inches. 





F. 



inches. 







212° 



29 89 



1-0 



332° 



216-21 



7 21 



222 



36 35 



1-21 



342 



247 '38 



8-25 



232 



43 91 



1-47 



352 



281-99 



9-40 



242 



52-72 



1-75 



362 



320-28 



10-68 



252 



62 '92 



2-10 



372 



362 -50 



12-08 



262 



74-69 



2-50 



382 



408 -92 



13 63 



272 



88-18 



2-94 



392 



459 -80 



15-33 





1 AO • KO 



lUo DO 



Q >A K 

 O 40 





DlO 41 



ih.io 



1/ lo 



292 



121-08 



4-04 



412 



576 -02 



19-20 



302 



140-88 



4-70 



422 



641 -90 



21-40 



312 



163 -18 



5-44 



432 



713 -32 



23-88 



322 



188-22 



6-27 









Thus, while an increase of 50° F. to the temperature of water vapour 

 at 212° causes an increase of pressure of only 1^- atmospheres, the 

 addition of another 50° gives an additional pressure of nearly 3 atmo- 

 spheres ; of another 50° gives 5 atmospheres ; while 50° more gives a 

 further increase of atmospheres. 



This rate of increase of pressure is nearly proportionate to the 5th 

 power of the excess of temperature above —40° F. Pouillet em- 

 ployed empirical formulae to ascertain the probable pressure at higher 

 temperatures up to 51b° C. These, although not mathematically 

 exact, are sufficiently so for our purpose — at all events up to the tem- 

 perature of 773° F., the critical point of water, at which new condi- 

 tions would be involved. 



Temperature. Pressure in atmospheres. 



510° F 50 atmospheres 



592 100 



686 200 



747 300 



794 400 



832 500 



864 600 



893 700 



918 800 



942 900 



962 1000 



At the critical point of water the pressure would be nearly 350 

 atmospheres, or if the rule holds to the temperature at which water 

 may undergo dissociation, we should have a pressure exceeding 1000 

 atmospheres. In any case these conditions point to a possible term 



