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Chemistry. — "Thr //ni/iiii/ iminis nf sulnrufi'd m'/»//"/<.v in binary 

 systems in irJilrh a. ronipoiind occurs". By Prof. H. W. 

 Hakhiis Roozeboom. 



(tlommunicated in the meeting of November 25, 1905). 



In a previous communication ') it has been ascertained what 

 branches in the- three-phase lines for solid, liquid and vapour may 

 occur in binary systems in which a solid compound appears, namely 

 for the three cases that : 



a. the va])Our ])ressure of the licpiid mixtures diminishes gradually 

 from the component ,1 to tlie component B ; 



b. liquid mixtures occur with a minimum pressure; 



c. liquid mixtures occur witli a maximum pressure. 



For the right understanding of the behaviour of such systems it 

 is particularly desirable to ascertain what is the order of the pheno- 

 mena which appear with ditferent mixing proportions of the components 

 when these, at a constant pressure, are brought from low to high 

 temperatures. 



If those ]iressures are very low the mixtures, at a sutïiciently 

 low temperature, are completely solid, and on elevation of the 

 temperature, they pass gradually and, at last, completely into vapour, 

 therefore simply a sublimation occurs. 



If the pressures are sutHiciently high (in the case of components 

 which are not too volatile, 1 aim. is (piite sufticient), the solid sub- 

 stances pass gradually and. at last, completely into liqnid and these 

 liquids evaporate at slill higher temperatures. In this case, fusion 

 takes place first and evaporation afterwards. 



With moderate pressures, however, the melting and evaporation 

 phenomena partly coincide, namely when pressui-es are chosen which 

 occur on the three-phase lines of the components or the compound. 



What cases may be distinguished wiieii no solid compound appears 

 has been fully investigated previously, by me. ') 



Particular attention has been called to the fact that the three- 

 phase line of the component B may be sometimes intersected twice 

 at the same pressure, which is possible when this line exhibits the 

 branches \a and I^*, described in the previous communication. (See 

 line BD in tig. 1 and 6). In such a case two separate boiling 



1) These Proc. VIII, p. 455. I learned that Dr. Smits had also come to the 

 conclusion that the minimum on the tlu'ee-phase line did nol coincide with 

 point //. 



') Heterogene (lleichgewiclilc. Helt 2. p. 33S, el seq. 



