of Miscible Liquids by Distillation, 



645 



For mixtures containing less than 40 per cent, of benzene 

 this column did not yield a pure distillate. For such mix- 

 tures a longer column must be employed. 



4. The exposition which has been given of the principles 

 underlying the art of discontinuous distillation and the con- 

 firmatory experiments which have been described are an 

 essential preliminary to the investigation of continuous 

 distillation. 



In the continuous distillation of a binary mixture both 

 components are constantly removed and the liquid does not 

 become increasingly difficult of separation by reason of the 

 accumulation of one component. Table I. shows the mini- 

 mum flow of vapour and of liquid during ideal discontinuous 

 distillation. Table VII. shows in similar manner the mini- 

 mum flow in an ideal column during the continuous distilla- 

 tion of a mixture of equal masses of benzene and toluene. 

 The upper portion of the column behaves as in discontinuous 

 distillation, condensation taking place throughout its length, 

 but in the lower portion evaporation of benzene occurs and 

 the requisite quantity of heat to produce this evaporation 

 must be supplied. This heat may be supplied throughout 

 the length of the lower portion, as in the still devised by 

 Lord Rayleigh, or, if minimum flow be not essential, by sup- 

 plying a quantity of vapour of the less volatile constituent at 

 the bottom of the column, as in the Coffey still. 







Table VII. 





Temp. 



°C. 



C C H G 



per cent, 

 in liq. 



Grams Vapour 

 passing up 

 O e H 6 + C 7 H 8 =total. 



Grams Liquid 



flowing down 



C G H 6 + C T H b =total 



Top o 

 80-2 



f column. 

 103 



l-64+0;00=l-64 



0-64 + 00=0-64 



81-8 



90 



1-054- 007 = 1-72 



0-65+007=0-72 



83-5 



80 



1-65 +016=1-81 



0-65 + 0-16=081 



85-4 



70 



1-66 4-0-28 =1-94 



0-66+0-28=0-94 



87-6 



60 



l-06+0-44 = 240 



0-66+0-44=l-10 



90-0 



50 



1-664-0-66 = 2-32 



0-66+0-66= 1-32 





2 



grams liquid supplied 



1-66 + 1-66 =3-32 



93-0 



40 



l-l2 + 0'68= 1-80 



1-12+ 1-68=2-80 



964 



30 



073+0-70 = l-43 



0-73 + 1-70=243 



100-4 



20 



0-43-f0-71 = l-14 



0-43 + 1-71 =214 



105-0 



10 



0-19 + 0-72=0-91 



019 + 1-72=1-91 



1106 







0*004-0 75=0-75 



000+1-75 = 1-75 



. Mag 



. S. 6. Vol 



. 41. No. 244. .1/ 



ml 1921. 2 IT 



