( 186 ) 



the observed temperatures ; in fig. 4^ tlie reverse is seen, but all 

 tlie same it is seen that in the two ligures the same things are to 

 be met with in the succession of sections 1, 2 and 3. The three 



Fie. a. 



X 



Fig. 4&. 

 pressure cui-vc lies liigiiesi in 1 and 

 lowest ill 3. In 1 and 2 we (U) not 

 find any relrograde condensation, Init 

 retrograde solidification, and in 3 we 

 find retrograde condensation only. In 

 tig. 4:ti howe\er the plait[)ointpressure 

 increases in the order 1, 2, 3, and 

 decreases in lig. 4A, but tiiis is due 

 to the fact that in the first case the 

 order 1, 2, 3 means towards higher 

 temperatures, and in the second to- 

 wards lower. 



Concerning the course of the iso- 

 therms of soUibility above the three 

 phase pressure curve, van dkr Waals 

 has shown the probability of a course 

 as given in fig. 5, from u hich results 

 that the branch c s also sliows retro- 

 grade .solidificalion. Tliis case, in which 



