( 237 ) 



perature. Nor can his considerations of Dec. 1905 give an indication 

 to conclude to the occurrence of a minimum plaitpoint temperature 

 in the branch A', K m of the plaitpoint curve. For there van Laar 

 starts from the value of dT xp i dx at the critical temperature of the 

 most volatile component called 1\ by us. The condition that at 

 7'a- 2 , the lower of the critical temperatures of the components, 

 </7',,/ 'dx<^0, implies that if the plaitpoint curve crosses from K^ to 

 K x , a minimum temperature must occur in it : ) Van Laar (These 

 Proc. May '07 p. 43), considers now the value of dT xp i/dx for the 

 least volatile component (for A',). It is clear in our opinion, that at 

 the highest critical temperature the condition <IT, r i dx<^0, which 

 coincides with the tirst of the inequalities mentioned (cf. p. 797 

 last sentence of the alinea at the top), does not give any indication to 

 conclude to the occurrence of a minimum plaitpoint temperature. 

 That if for A', dT xl ,i/dx < 0, really one of the conditions for the 

 occurrence of a minimum plaitpoint temperature in the branch K x K m 

 of the plaitpoint curve has been fulfilled, van Laar has, in our opinion, 

 only shown by his considerations on the situation of the double 

 plaitpoint. not given until April (translated in These Proc. of .May) 

 at the same time with his remarks, which considerations agree with 

 those which had led us a month before to the statement of the two 

 conditions mentioned. 



*) Only if the plaitpoint curve crosses from A'! to An, this condition is sufficient 

 to conclude to the occurrence of the minimum plaitpoint temperature (cf. van 

 Laar p. 46); for if the branch of the plaitpoint curve starting from A'» bends 

 round to van Laar's point A {x=l, v=ö 23 in our notation), we cannot speak 

 of a minimum plaitpoint temperature in the sense which is generally attached to 

 this word. 



A similar consideration gave rise to our remark in note 2 p. 795, which 

 remark we are obliged to maintain in spite of Mr. van Laar's contradiction, 

 p 40. (Wrongly Mr. van Laar thinks there, note 1, that in our note instead of 

 "maximum-temp." "minimum-temp." should be read, which might also immediately 

 appear by comparison with the cited text of Verschaffelt). 



