1821.] Causes of Calorific Capacity, Latent Heat, fyc. 455 



determine the quantity which must be evaporated to reduce it ta 

 a. given temperature. 



Denoting, as before, the weight of the water by w, and 

 putting v/ for the quantity of vapour liberated, we have t' =. 



6ul 6 v> t , (t — t') 6 to _. _, x 



t: K — rrb = « ~ ; whence w' = ~ . Q. E. I. 



6(10 — »') + 11 to 6 jo + a itf 5 t' ^ * 



Cor. 1 . — Conversely the quantity lost by evaporation, and the 

 primitive temperature, being given, the reduced temperature may 



easily be found ; for it will be simply r' = 



6 to -i- 5 to'' 



Cor. 2. — By this theorem we can also determine the effect 

 which a given diminution of compression will have on the tem- 

 perature of water by suffering a portion of its vapour to escape. 

 From the views I have taken in a preceding part of this paper, the 

 greatest temperature water can endure, under a certain compres- 

 sion, is its temperature of ebullition. If the temperature be 

 attempted to be raised above this, ebullition takes place, and the 

 decomposition proportions itself to the accession of temperature, 

 so as to keep the temperature at about the same. Therefore, if 

 any part of the compression be removed, and the previous tem- 

 perature was higher than that of ebullition corresponding to the 

 reduced compression, ebullition will immediately ensue, and the 

 former temperature descend to the latter. In general, and par- 

 ticularly in high temperatures, this diminished temperature, or 

 temperature of ebullition, will not, as I have shown, materially 

 differ from the corresponding temperature of tension ; so that 

 we may hence substitute the one for the other without commit- 

 ting any great errors. By Prop. XV. if E equals the tension or 

 compression, and t' the temperature, E = 30 {-002783313 t' — 

 2-2637 14} 8a = <p t' ; and, therefore, t" = <p ~ ' E. Consequently 

 the new temperature is immediately known from the compres- 

 sion. 



The weight of vapour likewise lost is given in th same terms ;. 



„ , (t — t') 6 to (< — <j>-' E)6 to 

 for W = : — = ■ . 



5t' 5p-' E 



Cor. 3. — This theorem, and some of the preceding in the pre- 

 sent paper, enable us to develop several curious things respecting 

 cooling and diminution by evaporation, in functions of' them- 

 selves and the time ; but these things leading to very extensive 

 inquiries, I propose to consider them at another opportunity. 

 However, any one who wishes to pursue the subject will find 

 many of the phenomena involved in the equation — d T — 



. , 3 , d t' ; in which T is the time of departure from the 



primitive temperature t ; w, as before, the primitive weigh of 

 water; and -/the indeterminate temperature. 



Scholium. 

 I have sedulously looked over all the authors I have at hand 



