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V. 



A METHOD OF EXACT DETERMINATION OP THE CON- 

 TINUOUS CHANGE IN ABSOLUTE DENSITY OF A 

 SUBSTANCE, e.g. WAX, IN PASSING THROUGH ITS 

 FUSION STAGE. 



By WILLIAM J. LYONS, B.A., A.R.C.Sc. (Lond.), 

 Royal College of Science for Ireland. 



[communicated by pkofbssor w. brown, b.sc] 



[Read Febuuaky 22. Ordered for publication Makoh S. Published May 16, 1911.] 



Introduction. 



The simple apparatus described in this paper was designed some time ago 

 for the purpose of examining the volume-change which occurs on fusion in 

 the case of waxes. In such eases the melting-point is not definite; and it was 

 thought that the volume-temperature curve would indicate effectively the 

 limits of temperature within which the change of state occurred more or 

 less continuously, and would also reveal by the discontinuity of the curve 

 the purity or otherwise of the wax. For such purposes the change in volume 

 had to be observed continuously and for very small differences in temperature; 

 hence the dilatometer-form with graduated stem was adopted. The appa- 

 ratus gave very satisfactory results as to the relative change in volume 

 during fusion ; but it was soon recognized that a slight development of the 

 method would enable exact determinations to be made of the density of the 

 substance at any temperature above or below the fusion-stage, and would 

 give absolute values of a high degree of accuracy. The method is now 

 being employed by the author in a systematic investigation into the change 

 n density on fusion of a number of organic compounds which form isomeric 

 and homologous series; but it is thought desirable to make a preliminary 

 communication describing in detail the apparatus and its use, and the results 

 obtained for some samples of wax.' 



' For an excellent bibliography of the whole subject of change of volume on fusion, see 

 Chwolson's " Traite de Physique," 1910. Tome III., Second Fascicule, p. 652. 

 SCIENT. PROC. E.D.S., VOL. Xltl., NO. Y. L 



