( 808 ) 



below the middle })oiiil i"21)',<S. It ajipeared in other words, that 

 -with Young's still head an alniost perfect separation was reached 

 already in a single distillation. That the law nnder cojisideration 

 holds in this case, is self-evident. 



I fonnd also there where the 7'i-line is less steep, as for benzene 

 and toluene, that the thermometer remained in the neighbonrhctod of 

 the boiling point of the most volatile sub.stance during tiie greater 

 pai't of the distillation, and then suddenly rose rapidly, quickly passing 

 through the middle temperature, so that here too the breaking off 

 at the middle temjierature is not 'essential. 



Where it is essential as Avith distillations with less elKicient still 

 head or for mixtures with very flat T.c-Vuie, the law does not 

 hold. As an instance I give the three following distillations, the first 

 of Avhich, where a mixture with very steep 7^/'-line is distilled with 

 the evaporator, conforms to the law; whereas the second, where the 

 same mixture is distilled with an ordinary straight tube and sjtecially 

 the third where a mixture witjj flat 71/-line is distilled wifii the 

 evaporator, deA'iate from the law. 



Still head. 



('ompoiiont T'niiling point 



Weight of tlie 



components 



in sr. 



I Come over below midde 

 temp, in gr. 



In accordance witli lliis VorN(r himself gi\es liis law ojdy for 

 mixtures ^\lli(•ll arc not diriictill to separate distilled with an efficient 

 still liead. 



I tliiidv that I am juslificd in concluding that the law is simply 

 based on the separation of the mixture in its components, and that 

 we have to include nnder what Yorxo calls: a far from perfect 

 separation, only those cases, whei-e at the end of the distillation a 

 small fraction of the most volatile substance is left in the recipient 



