( 42 ) 



^ = T W '" , « (1 -'''" )(1 -- )5 (8) 



Hence we eau immediately calculate x tt and 'J\ from (7) and (8) 

 for any given set of values of 6 and it, or tp and n. 



3. For our ease («j small) it is now important to know, when a 

 minimum occurs in the plaitpoint line C C\, when not. For this 

 purpose we shall derive the condition that the minimum is to appear 

 exactly in the point C a . Evidently this condition will then indicate 

 the limit between the two cases that there occurs a minimum in 

 the neighbourhood of C\ or not — in other words whether the line 

 of the plaitpoint temperatures in C s descends first and rises later 

 on to T in C\ ; or whether there is an immediate rise from T 2 to 

 T„. (We call to mind that with us T s is always the highest of the 

 two critical temperatures T l and T a ). 



Now y = - = - in the point C 2 , while x = l. Hence equation 

 v 3 



(2) passes into 



(l_ s )«(l_3,j)» 81 (1 — zy 



(<P + i) 2 = 



4X7, (7 3 -~~) 2 (Gc'-8s + 27,) 10(2-3=)' 

 from which follow s : 



9(1-*)» 



hence 



w 4-1 = 



v t 4 2 _ Sz 



[/a, if (1-3*)' W 



From 



2 ■=. nu> (y> -4- *) 



b x b, b x 1 1 

 follows further, as to = — = — X .— = „z—r and a; = J 



1 7i 3 n (1— *) a 



(flP + 1) = 



This \ ïelds : 



3 1+w 4 1+// 2—3* 



l + «_3 (1— zf 

 n ~4«(2— 3z)' 



&, 3 (1— *)' 



- = 1 + « = - — — — — — (b) 



6, (1— 3s) (3 — 5s) 



When we put: 



