PAPER BY PROF. BEZOLD. 221 



designated hj p^ as being located on the curve of saturation, the equa- 

 tion is 



1', 

 or tinall}' after substituting tlie value of v, 



^'- xKb ^ ^ 



It is therefore easy to determine the correlated values of t\ and p, for 

 any constant quantity of moisture x and for any given temperature. 

 On the other hand, only with the greatest difiiculty and even then only 

 by the use of empirical formuhe is it possible to bring the curve of 

 saturation into the ordinary form:* 



F {v„ p,)=0. 

 t 



We also will therefore entirely relinquish all attempts in this direc- 

 tion. By so much the more important is it therefore to show that from 

 the curve of saturation for a given value of x one can with ease (Induce 

 such curve for any other quantity of moisture. If T and hence also e 

 is constant, then it directly follows from the equation 



RsT 



v,=x 



e 



that the initial abscissas of isotherms corresponding to equal tempera- 

 tures but diflerent quantities of moisture are proportional to these 

 quantities of moisture themselves, or if we indicate by Vi and r> the 

 initial abscissas belonging to the quantities of moisture Xi and .r2, we 

 have 



Vi : Vy=Xi : x-i. 



If therefore we have any j)oint such as Ni of the dew-point curve /Sj 

 corresponding to a given temperature T this will be the initial point of 

 the isotherm (T, .r,) if as in the above given manner we indicate the 

 point corresponding to the temperature T and the quantity of vapor 

 j?i; now draw the isotherm (T, Xi) for the same temperature T but for 

 another quantity of vapor .r2, then we have onlj- to increase or diminish 

 the abscissa of ^"i in the ratio x^: Xi in order to obtain the X2 of the 



* We see this from the following consideration: Since a-ccordiug to equation (4) 

 e=<p (jJs, X), and since again e^F{T), and moreover T=ip (ps, x); since further the 

 equations (3; and (4) give Vs ps^B\-\-x lis) T, therefore v^ Ps^(Bk-^x Bs) . ip {[},, x), 

 or if we omit x from under the functional sign as heing constant, 



V, ps—{R\+xRs). tp{p,) 

 an equation which contains only )•, and p,, hut not explicitly, as variables. 



