( 620 ) 



There, the end term of the nioiioclinic mixiiif>' series is situated 

 still miicii closer to the axis than in the case mentioned. In conse- 

 quence of the very great difference in solubility of the CI-, and the 

 /-compound we never obtain here from alcoholic solutions anything 

 else but rhombic very delicate needles, while the monoclinic phases 

 crystallise so indistinctly that they are quite unsuitable for a serious 

 investigation. 



The Br-, and the /-ester readily crystallise together in all propor- 

 tions with angular values which differ but little from those of the 

 components. No optical anomalies could be found in such mixed 

 phases. From this it follows that to those two halogen substitution 

 products belongs an analogous molecular structure. Their molecular 

 volumes in the solid condition agree indeed vei'y well ; the difference 

 is smaller than between that of the CI-, and i??"-compounds. 



As regards the lowering of the melting point of the compound 

 melting at the higher temperature by addition of the one melting 

 at the lower temperatui-e, this is not proportionate to tlie number of 

 added molecules, as in the system Br- -|- /-compound. In the 

 mixtures of CI- and J-ester, the observed values are always situated 

 on a curve which occurs above the line of the pi-oportionate lowering 

 of the melting point; in the system CI- and /?r-ester, on a two- 

 periodic curve which occurs below the said straight line. 



It must also be observed that the mixed pluises deposited from 

 alcoholic solutions possess a larger content in the compound melting 

 at the higher temperature than the solution from which they have 

 formed. For instance, from a solution containing 20 7o of -Br-ester 

 and 80 7o of C7-ester, mixed (rhombic) crystals were at first depo- 

 sited which melted at 57° corresponding with a considerably higher 

 percentage of the ^/'-compound. 



The C/d/oro-compound which is monoclinic with : 



a:b:c = 1,8626 : 1 : 3,4260, and /? = 64''18' 

 and the forms : 



a=|100}, c=|001j, »-=|T02{, p=j2 1 0|, ü=<01 IJ, o=|Tll|, ,i;=jl 1 1|, m=\\\?,\. 

 presents a habit which is not at ail like that of the two other deri- 

 vatives, although that habit, as shown in fig. 1 — 5, is in a high 

 degree variable, according to the choice of the solvent and tempe- 

 rature of crystallisation. 



The habit of the Br- and /-compound is on the otiier hand per- 

 fectly analogous ; in the /-ester it is, moreover, very constant under 

 different conditions of crystallisation (fig. 8) whilst it is still some- 



