368         PREPARATION  AND  PURIFICATION   OP  BENZOLE. 
diet  by  those  near  whose  abode  it  grows ;  and  the  white  inner 
part  of  the  stem  of  the  full-grown  plant,  which  reaches  the  stat- 
ure of  a  man,  is  conside»ed  a  delicacy  when  roasted  and  flavored 
with  salt  and  butter.  * 
The  annual  value  of  the  asafoetida  trade  with  India  is  estima- 
ted in  the  Government  Reports  of  the  North  West  Provinces  at 
about  £2,200. — London  Pharm.*Jour.\  May  l$Zl8d4,  from  The 
Technologist. 
ON  THE  PREPARATION  AND  PURIFICATION  OF  BENZOLE. 
By  M.  E.  Kopp. 
I  have  elsewhere  mentioned  the  superheating  process  by  which 
we  have  succeeded,  more  or  less  perfectly  in  converting  the  heavy 
tar  oils,  and  which  are  frequently  much  charged  with  napthaline, 
into  lighting  gas  and  volatile  oils  rich  in  benzole. 
The  apparatus  for  this  transformation  consists  of  a  horizontal 
retort  of  cast  iron  or  earthenware,  so  arranged  that  it  can  be 
heated  to  incipient  redness  by  the  furnace  flame  and  gases  cir- 
cling round  it.  One  extremity  of  the  retort  is  formed  by  a  cover, 
easily  adjusted  and  removed,  giving  access  to  the  interior,  and  al- 
lowing of  the  necessary  frequent  cleaning  out  of  the  retort. 
At  a  certain  distance  from  the  other  well-closed  extremity  is  a 
partition  half  the  height  of  the  retort,  intended  to  prevent  the 
flow  of  oil  outside  the  retort. 
Beyond  this  partition  the  retort  communicates  with  a  watery 
chamber  by  means  of  a  tube  placed  at  the  most  inclined  part  of 
the  side. 
The  lower  part  of  the  water  chamber  communicates  by  a  hy- 
draulic syphon  with  a  waste  pipe  placed  at  its  extremity,  serving 
to  collect  the  heavy  and  little  volatile  oils  which  condense  in  this 
water  chamber.  But  the  upper  part  of  the  chamber  is,  moreover, 
in  communication  with  a  good  refrigerator  of  the  usual  construc- 
tion, into  which  pass  the  more  volatile  products,  which  there  sep- 
arate into  light  oils,  which  condense,  and  are  collected  apart,  and 
into  lighting  gas,  which  flows  into  a  gasometer.  The  operation 
is  conducted  in  the  following  manner  ; — 
The  retorts  (a  series  of  which  may  be  placed  in  the  same  fur- 
nace, and  which  may  communicate  with  the  same  water  chamber 
