ON  THE  MANUFACTURE  OF  OLEUM  iETHEREUM.  127 
On  commencing  the  manufacture  of  Oleum  iEthereum,  the 
writer  had  no  practical  experience  to  guide  him,  and,  of  course, 
had  to  rely  on  the  observations  and  experience  of  others  for 
information.  Among  others,  the  papers  of  Dr.  E.  R.  Squibb, 
Journal  of  Pharmacy,  vol.  v.  3d  series,  p.  194,  and  Proceed- 
ings Am.  Pharm.  Association,  1860,  were  found  to  give  the 
most  explicit  information  on  the  subject,  and  served  as  a  guide 
for  the  comparison  of  results. 
At  the  U.  S.  Army  Laboratory,  Philadelphia,  the  manufac- 
ture is  carried  on  in  glass  retorts  of  the  best  French  make,  and 
of  a  capacity  of  seven  to  eight  gallons.    They  are  heated  by 
means  of  a  sand  bath  fifteen  and  a  half  to  sixteen  inches  in 
diameter  and  twelve  inches  deep ;  the  depth  of  the  sand  under 
the  retorts  is  never  more  than  half  an  inch,  and  does  not  come 
up  on  the  sides  of  the  retort  more  than  about  five  inches. 
This  facilitates  the  cooling  of  the  retort  in  case  it  is  desirable. 
The  mixture  introduced  into  the  retort  consists  of  equal  mea- 
sures of  95  per  cent,  alcohol,  and  sulphuric  acid,  sp.  gr.  1*845, 
care  being  taken  to  allow  all  the  sulphate  of  lead  to  separate 
before  introducing  the  mixture.    The  charge  for  a  retort  of 
seven  gallons  capacity  is  six  and  a  half  gallons ;  the  refrigera- 
tion is  effected  by  means  of  a  large  Liebig's  condenser,  and  the 
distillate  is  collected  in  a  tubulated  receiver,  which  is  so 
arranged  that  the  distillate  will  enter  through  the  tubulure, 
and  the  incondensible  gases  will  pass  through  a  tube,  connected 
with  the  large  end  of  the  receiver,  inco  the  chimney.  The 
joints  are  made  air-tight  by  means  of  cork  and  India-rubber 
tubing.    The  sand  baths  can  be  heated  in  a  very  short  space 
of  time,  the  furnace  being  of  an  excellent  construction,  and 
the  flues  of  which  make  a  complete  circle .  around  the  sand 
bath  before  entering  the  chimney,  with  an  excellent  draft.  It 
is  necessary  to  give  a  detailed  description  of  the  apparatus  em- 
ployed to  permit  of  a  thorough  appreciation  of  the  difficulties 
experienced  at  the  laboratory. 
At  the  suggestion  of  Prof.  J.  M.  Maisch,  of  this  laboratory, 
an  accurate  account  of  the  temperatures  at  which  the  distilla- 
tion proceeded  from  hour  to  hour,  during  the  day,  was  kept 
