( 636 ) 
Chemistry. — „On the melting of binary solid mixtures by cooling”. 
By Prof. H. W. BAKHUIS ROOZEBOOM. 
(Communicated in the meeting of March 29, 1902). 
The phenomena which may occur when mixtures pass from one 
state of aggregation into another are as a rule of a much more 
complex nature than those which take place with a single substance. 
For this reason a number of cases have been discovered in which 
the succession of the states of aggregation is wholly or partially reversed. 
The earliest known instance is met with in the phenomenon of 
retrograde condensation, where a binary liquid is first formed from 
vapour by increase of pressure at a constant temperature and then 
passes again into vapour. 
A similar reversion occurs with ternary liquid-mixtures when 
these on evaporation first deposit a solid substance and then redissolve 
the same. }) 
We may also consider in this ight my recent communications on 
saline solutions with two boiling points.*) Here, the possibility of 
a solution commencing to boil by cooling was shown to exist. 
I will now mention a case where a binary mixture first solidifies 
on cooling but then again partly liquefies by further cooling. 
The possibility of such a phenomenon first occurred to me during 
my theoretical study of the changes of binary solid mixtures. °) 
Among the. large number of types which I then distinguished 
were found a few instances (le. fig. 15 and 20) where mixed 
erystals, on cooling, undergo a transformation and break up into 
another solid phase and liquid. For want of some detailed example 
of transformation of mixed crystals, I did not further investigate 
these special cases although it seemed to me that one of these 
might possibly be found during the study of the so-called liquid 
erystals. A case where mixed crystais occurred in the liquid crystalline 
condition had been investigated shortly before by SCHENCK who had 
found such a mixing between azoxyanisol and benzophenone. My 
surmise has now been completely confirmed and Mr. pE Kock who 
is engaged with a dissertation on this subject has had the good 
fortune to meet with a very striking example in mixtures of 
azoxyanisol and hydroquinone. 
*) ScHREINEMAKERS, Zeit. phys. Chem. 10.467 and Morr ibid 27.214. A good 
many allied examples are found in binary and ternary systems with two or three 
liquid-layers. 
*) Rep. Meeting 28 Dec. 1901. 
5) Zeits. phys. Chem. 30. 413 (1899). 
