( èoi ) 



titles : - ,-, siii'fa(*(^ (Iislaiice spliores; , ^^''^'Ji <»f i^'i''f;^<'<^' '»t iinrtact; 



total ' jolal ' 



availalile voliiiin', is more acciiralclv known, wh» sliall Ite justified 



in e\]»e('lin,u- hollei' conconlance of expei'inient and theory. 



Physics. — " Xott' mi, Sydnky Young's Imr of disl /'!/(( t/'ou." By 

 Miss .1. Rkl'dlkr. (Communicated by Prof. J. D. van der 



Waals). 



St>me time ago Sydney Young gave a law of fractional distillation^), 

 Avliicli seems very strange at first sight. According to this law in 

 distillations w itli an efficiënt still, the weight of distillate coming ovei- 

 below the middle point of the boiling temperatures of the components 

 would be almost equal to the weight of the most volatile component, 

 also when the sepaiation is far from [)erfect. This concordance 

 would be so close, that Young could even Imse a general law of 

 (piantitati\'e analysis on it, at least for substances whose boiling 

 points were not too near to each other. Now it seemed, howevei-, 

 unlikely, that this law should always hold, (pute imlependent of the 

 nature of the 7^/'-curves and of the c(un|)osilion of the mixture 

 from which we start. Therefore I have distilled some mixtures, 

 inter alia also with Young's evaporator still head. 



I begaji with some of the examples chosen by Young, and I fonnd 

 i-eally thai they cojilii-med the law. Then I ti'ied to determine the 

 limits of its validity by takijig a mixture with very steeji 7'/'-liue, 

 so that 1 could closely examine, what liap|»e]is, wluui the distillation 

 is broken off aboxc or below the mean boiling point. I took for 

 this bt^n/ejie (boiling point 79°, 6) and aniliiu^ ;boiling point '\8(f) 

 and began \vitli sncli a composition, that the initial l)oili]ig jmint 

 lay already above the middle point, thinking that Young's law would 

 be sure not to hold in this case. Yet also now the law was confirmed, 

 but the process of the distillation revealed also the character of the I'ule. 

 For it a[)])eared that independent of the com|>osition of the mixture, 

 even when it consisted of 4 " „ benzene and 9(j "/„ aniline, and so 

 a thermometer, which I had placetl in the licpiid, |>oinled to almost 

 180'' already in the begimiing of the distillaticui, the temperature in 

 the still head remained constant at 79" for a long time, and rose 

 then suddenly very rapidly to 18(J , so that the distillation might 

 have been broken off with the same result verv far above and 



1) J. Ghem. Soc. 81 752. 



