( 455 ) 



selves the transition of case A into case C. In case A in which the 

 rate of the clocks diifers greatly, the manner of motion which is most 

 difticult to realize in case C, namely the one, where the clocks have 

 each their own rates, is the normal one. Yet the two other manners 

 of motion also ai-e possible, i. e. those where exclusively one of the 

 principal oscillations appears ; however in these cases, the pendulum of 

 the least active of the two clocks will still perform a slight oscillation 

 though not sufficient to set its motive work in motion. 



If now starting from case A we reach case C, i. e. if the rate of 

 the clocks is taken more and more equal, the state of motion with 

 mutually different rate of the clocks becomes continually more diffi- 

 cult to realize, finally perhaps impossible ; whilst for the two other 

 possible manners of motion the pendulum of the second clock too 

 keeps performing greater and greater deviations till these deviations 

 are finally sufficient to set its motive work also in motion, so that 

 both clocks go quite alike, either with the rate belonging to the rapid 

 principal oscillation or, what is more easily realized, with that oi 

 the intermediate one. 



Chemistry. — "The different branches of the three-yhase lines for 

 solid, liquid, vapour in binary systems in which a compound 

 occurs." By Prof. H. W. Bakhuis Roozeboom. 



(Communicated in the Meeting of October 28, 1905) 



A chemical compound, formed from two components, need not to 

 be regarded as a third component, when this compound is somewhat 

 dissociated, at least when it passes into the liquid or gaseous state. 

 Instead of the triple point we then get a series of triple points, the 

 three-phase line, indicating the co-related values of temperature and 

 pressure at which the compound can exist in presence of liquid and 

 vapour of varying compositions ^) This was advanced for the first 

 time in 1885 by van der Waals. The equation for that line was 

 deduced by him *) and shortly afterwards ") applied by me in a few 

 instances where it was always admitted that the vapour tension of 

 the liquid mixtures gradually diminished from the side of the most 

 volatile {A) towards that of the least volatile component {B). 



In the first considerations as to the course of the three-phase line 



1) There exist several other three-phase lines which are not considered here. 

 ^) Verslag Kon. Akad. 28 Febr. 1885. 

 a) Rec. Tr. Ghim. 5, 334 (1886) 



