APPARATUS  FOR  PREPARING  ETHER  BY  STEAM.  387 
For  discharging  the  still,  the  cork  and  tubing  are  removed, 
and  the  pipe  bent  down  at  d.  This  obviates  the  necessity  of  the 
troublesome  plugs  and  stop  cocks. 
e.  A  cylinder  of  sheet  lead,  of  6  lbs,  to  the  square  foot,  is 
made  of  a  diameter  to  correspond  with  that  of  the  inside  of  the 
pan  at  the  surface  of  the  stand.  The  joint  or  seam  in  this  cy- 
linder is  made  by  "  burning  "  the  two  edges  together,  either  by 
red  hot  irons,  or  by  Dumas'  inflamed  jet  of  hydrogen,  but  best 
by  the  irons,  as  this  makes  a  more  solid  joint.  The  lower  edge 
of  the  cylinder  is  rasped  off  upon  a  bevel  corresponding  to  the 
inclination  of  the  sides  of  the  pan,  and  the  rim  of  the  pan  is 
scraped  bright.  The  cylinder  is  then  set  in  its  place,  and  turned 
a  few  times  till  the  contact  is  as  perfect  as  possible,  when  the 
outside  sulcus  is  filled  up  with  solder  and  «  wiped  "  smooth. 
A  shoulder  is  next  turned  upon  the  upper  edge  of  the  cylinder, 
and  the  cover  and  head  formed  and  soldered  in  place  without 
unusual  precautions,  as  the  acid  never  reaches  the  solder  of  these 
joints  injuriously. 
/.  A  hole  is  then  bored  obliquely  into  the  still  at  /,  and  a  piece 
of  f  inch  lead  pipe  fitted  tightly  into  it  and  soldered  outside. 
Into  this  lead  pipe  a  tubular  thermometer  is  passed,  and  the 
space  between  the  lead  and  the  glass  through  the  whole  2  inches 
of  pipe  well  filled  with  a  putty  made  of  carbonate  of  lead,  or  of 
sulphate  of  baryta. 
g.  Another  short  piece  of  1\  inch  thin  lead  pipe  is  soldered 
on  at  g,  for  charging.    This  is  stopped  with  a  cork. 
h.  On  the  front  of  the  cylinder,  about  13  inches  above  the 
rim  of  the  pan,  a  circular  piece  of  sheet  lead  is  soldered,  like  a 
patch,  so  that  the  parietes  may  be  double  thickness  there. 
Through  this  patch  or  outer  layer  only,  a  hole  li  inches  in  di- 
ameter is  bored,  by  means  of  a  brace  and  bit.  Through  the 
inner  layer,  or  proper  wall  of  the  cylinder,  a  hole  1  inch  in  di- 
ameter is  bored,  upon  the  same  center  as  the  first  hole.  This 
leaves  a  rabbet  of  J  inch  all  round  the  inner  hole,  into  which  a 
piece  of  retort  bottom  or  other  thin  glass  is  fitted  and  well  puttied. 
This  forms  a  very  convenient  window  by  which  to  regulate  the 
feeding  cock  during  the  process.  The  quantity  of  the  charge 
should  be  so  regulated  that  the  surface  of  the  acid  liquid  when 
heated  to  boiling  should  come  nearly  up  to  the  window,  or  be 
