PAPER BY PROF. PEZOLD. 



261 



T1F1, T 2 F 2 , etc.; in the figure the origin is omitted. We see at once 

 that F-i lies on the straight line drawn through F Y and F-, and that 



T l T 3 _ T 3 F 3 -T l F 1 m, 

 T 2 T 3 -T 2 F 2 -T 3 F 3 ~m 1 



In order now to obtain a decision as to the degree of saturation, we 

 must also introduce into the diagram, as ordiuates, along with the 

 values of?/,, y,, and y 3 , also the values of?//, y 2 ', and y/, corresi)onding 

 to complete saturation. The ends of these ordinates, which are repre- 

 sented by Fi', F 2 ', and F z ' in the diagram, all lie upon a curve that with 

 increasing t rises rapidly, and the equation* of which is 



2/ = 623 /i~-(U77, 



when for ft we insert the proper constant pressure. 



With the assistance of this equation, or with the approximate for- 

 mula obtained by development, 



y= 023^ + 234.88 (J J 



the tables communicated in the appendix [page 287J have been com- 

 puted, by the help of which the curves can be easily constructed di- 

 rectly for the pressures therein considered, and which we can designate 

 as curves of the quantity of vapor needed for saturation at the pres- 

 sure ft [or for brevity, tlie saturation curve]. 



It will now suffice to cast a glance at the figure in order at once to 

 obtain the following propositions: 



(1) So long as for given temperatures t y and t 2 , the values 



* 



ii = p l and J ' 2 / = p.,, remain within given limits, the straight lino F x F 2 



passes entirely beneath the saturation curve, aud therefore there can 

 be no mixing-ratio for which conden- 

 sation can occur. 



(2) When p x and p 2 increase so much 

 that the straight line Fi F 2 touches or 

 cuts the saturation curve, as in figure 

 (38), then there occurs either one or 

 many mixing-ratios that may bring 

 about condensation. , r 



(3) When J R, = 7?,=100, ie.,when the J? J 

 two quantities ol air to be mixed are J% 

 saturated, then the straight line F { F\ 

 coincides with the curve F x ' F 2 , and 

 then for every mixture theie occurs -^ / 

 super-saturation or condensation. 



Fi.J. 38 



Harm, Zeit. Oeaterr. Gesell. Met, 1874, vol. ix, p. 324. [Smithson Rep., 1«77, p. 399.] 



