( ^-t: ) 



very strongly pronounced ; tlicreforo I Inive invcsliu.atr'd wlietlier 

 perliaps the compulation liad predicted it for mixtures of' N^O and 

 CjHg, for whicli tiie minimum critical temperature is probably much 

 lower than that of the components. I really find on the side of ethane, 

 the component with the lowest critical temperature, « = — (),(>19, 

 hence a negative \alue, which I'eiidei's (he existence of a minimum 

 oi'itical temjiei-ature necessary. 



5. After having shown by means of these few instances the 

 usefulness of formulae (4) for our purpose, I shall now closely 

 examine the course of the critical lines, in order thence lo deduce 

 •which conditions must be fullilled by the critical elements of the 

 components, in order that the mixtures may show definite phenomena. 



The shapes of these curves in the /y7' diagram have been deduced 

 by v.\x DER W.\ALS from formulae (1) and (2) ') with the single 

 simplification f>i, = h i^n -\- ^i,)- What we shall find here will there- 

 fore be a special case of the more general forms found by van dek 

 Waals, namely the transition between the two cases a'^,'^ a^^ a,^ 

 and '>\., <C "ii "21' investigated by him. 



J xlc Pxk 



If we put T rr: — — and jt = — and moreover introduce the new 



-' oh. Pok 



variable : = V'^jt, we may in our case write the e(piation of the 

 critical line: 



c'r, (1/^,-1 )-.T(.-r,-r,) + r(.T,-T, J/;'r,) = 0. . . (6) 



In the :x diagram therefore the critical line is a portion of a 

 hyperbola (see lig. 1), except when rrj =z r,, for then it is a portion 

 of a parabola (represented in fig. 1 by OAB; a straight line in the 

 ^^y diagram), and when jTj := 1 or K-t, = t,, for then it is a 

 straiglit line {CD and OE). 



In our drawing (fig. 1) one of the components always lies at the 

 point ^1, and we see that the form of the critical line is only deter- 



mined bv the relations — and — . Besides, when we move the 



Tok Pole 



second component along one of the critical lines, the shape of that 

 line remains unchanged. ") 



Fig. 1 therefore rejn-esents the forms which the critical line can 

 adopt in our case. In order to show that the observed forms agree 

 with these in a satisfactory way, I ha\e drawn in the same figure 

 'i the critical lines derived from the observations. The lines for 



1) Versl. Kon. Akad. Nov, 1897. 



-) As VAN DEW Waals; (laci cit,) has renwrkcd in general. 



