( 601 ) 



FC and C'R, wliicli al (' = 06' join al aii aii,ui(\ TIn» lop lino i-elatcs 

 to luoiiocliiiic, llio lowcM" one to rliomhic. siil|»liiir. 



Mixtures of O- 50 aloinic "/„ siilplim- mav on coolin,!»', <iive as 

 solid phases Cl,, S,C1, and SCI,. 



Tlie manner in which they are successively deposited nuiy he 

 best explained by tirst obsei'vin,i>- in what manner the soliditication 

 of a mixture of these three sul)stances would lake place when the 

 SCI, couhl be considered as an independent third component. 



This would be the case if this compound did not dissociate in the 

 lirpiid condition and also was not formed from liquid S,(J1., and CI,. 

 The system would then behave as a ternary system, the solidification 

 phenomena of which could oidy be c()m|>letely represented by a 

 spacial figure. 



We may also, however, disregard the constitution of the liquid 

 and express its gross composition only in CI, and S,^,^ whicli is 

 all the more justifiable as there is no means of determining the 

 amount of S(U., in the presence of CI, and S,C1,. 



We then obtain a repi-esentation in a plane (see fig. 2) which is 

 the projection of the spacial figure ^). 



In this figure EH and HA 

 are the solidification lines of 

 the binary mixtures SCl^ and 

 Cl„ EK and KD those of SCI, 

 and S/.I,, AG and DG those 

 of CI, and SjCl,. 



The ternary mixtures whose 

 conqiositions lie within the 

 region IHAG first deposit solid 

 chlorine, those in HvDG solid 

 S,CL and those in HEKI solid 

 SCI4. For each gross composi- 

 tion there exists a greater or 

 smaller series of molecular 

 arrangements which cannot be 

 represented in the plane, but on 

 which the temperature at w liich 

 the one or other solid phase 

 commences to be deposited depends. (Some mixtures may even sepa- 

 rate more than one phase according to their molecular composition). 



T 



JC£^ 



FiR. 2. 



6,<^^ 



1) We .must then accept as components: 3 GL and S^Clg in order that the 

 middle of the abscissa a.\is repiesents tlie composition SCIj. 



40* 



