ON  A  PROCESS  OF  FRACTIONAL  CONDENSATION.  453 
such  proportion  of  the  less  volatile  bodies  as  may  be  carried  for- 
ward with  them.* 
In  the  new  process,  perfect  control  of  the  temperature  of  the 
vapors  is  secured  by  simply  conducting  these  vapors  upward 
through  a  worm  contained  in  a  bath,  aa,  figs.  1  and  2,  the  tem- 
*  The  only  apparatus,  of  which  I  have  any  knowledge,  which  can  be  re- 
garded as  bearing  any  analogy  to  my  own,  is  that  employed  in  the  recti- 
fication of  alcoholic  spirits,  on  a  manufacturing  scale.  In  one  of  the 
older  forms  of  this  apparatus,  that  of  Solimani,  to  which  my  attention  was 
first  called  by  a  friend,  after  my  process  had  been  in  use  more  than  a 
twelvemonth,  the  temperature  of  a  dephlegmator  is  kept  within  such 
limits  as  to  give  alcohol  of  any  required  strength  more  readily  than  by 
the  common  methods.  The  mode  of  construction  of  this  apparatus  is, 
however,  only  adapted  to  manufacturing  purposes,  and  it  could  not  be 
utilized  in  the  more  exact  experiments  required  in  scientific  research. 
Either  on  account  of  its  complication,  or  some  other  cause,  the  apparatus 
of  Solimani  has,  I  believe,  long  since  been  abandoned. 
Mansfield  [Quarterly  Journal  of  the  Chemical  Society,  1849,  i.  264),  ob- 
serving that  "  the  boiling-point  of  benzole  is  the  same  as  that  of  alcohol 
of  sp.  gr.  0'825,"  remarks  that  "  any  of  the  summary  processes  of  rectifi- 
cation which  are  practised  by  distillers  in  the  manufacture  of  alcoholic 
spirits,  are  applicable  to  the  separation  of  benzole  from  the  less  volatile 
fluids  of  naplitha;"  and,  appended  to  his  scientific  treatise  on  coal-tar, 
under  the  title  "  Of  a  Practical  Mode  of  preparing  Benzole''  goes  on  to 
describe  a  process  for  that  purpose,  which,  I  believe,  he  had  previously 
pate.ited.  It  appears  that  Mansfield  did  not  employ  this  process  in  his 
research,  but  obtained  his  benzole,  as  well  as  the  other  less  volatile  hy- 
drocarbons, in  the  usual  manner,— by  simple  distillation. 
In  the  belief  that  no  process  of  fractioning  at  all  analogous  to  mine  has 
ever  been  employed  in  scientific  research,  and  that  I  am  not  in  any  way 
directly  indebted  to  any  of  the  devices  of  my  predecessors,  I  have  taken 
no  special  pains  to  consider  these  devices  in  much  detail.  I  may  say, 
however,  that  I  have  found  no  record  of  any  one's  ever  having  employed 
the  oil  bath  and  a  separate  fire  to  regulate  a  heated  condenser,  this  being 
the  essential  feature  on  which  the  superiority  of  my  process  is  based; 
adapting  it  at  once  to  both  high  and  low  temperatures,  and  for  the  most 
delicate  work. 
The  employment  of  bulbs,  above  referred  to,  as  proposed  by  Wurtz,  is 
simply  a  modification  of  the  old  process.  The  bulb  apparatus  furnishes 
the  same,  or,  at  most,  but  slightly  better  results  than  a  simple  retort ; 
being  no  more  than  equivalent  to  increasing  the  height  of  the  sides  of  the 
retort  itself,  without  introducing  any  control  over  the  accuracy  of  the  re- 
sults ;  the  only  advantage  gained  being,  that  these  results  are  obtained 
somewhat  more  quickly. 
