198  OLEUM  iETHEREUM  AND  SPIRITUS  2ETHERIS  COMPOSITUS. 
to  225Q,  and  while  hot  measures  6  f.^  more  than  the  sum  of  the 
ingredients.  When  cold,  however,  it  measures  15  f.3  less  than 
when  hot,  or  9  f.^  less  than  the  sum  of  the  ingredients.  After 
standing  twenty-four  hours  the  mixture  should  be  clear,  and  of 
a  very  pale  brown  color  with  a  pink  tinge,  or,  if  the  alcohol  is 
very  good,  should  be  as  nearly  colorless  as  though  the  acid  had 
been  diluted  with  so  much  water.  On  the  other  hand,  if  the 
alcohol  contains  much  grain  oil,  the  mixture  will  be  of  a  pink  color 
inclining  to  purple.  The  decantation  should  be  very  carefully 
performed,  so  that  all  the  precipitated  sulphate  of  lead  may  be 
excluded,  and  the  retort  should  be  of  such  a  size  as  to  be  three- 
fourths  filled.  The  retort  should  be  fitted  with  a  thermometer 
(bulb  immersed  in  the  mixture)  in  the  tubulure,  and  should  be  so 
placed  on  the  sand  bath  that  all  parts  of  the  neck  incline  toward 
the  condenser.  It  should  be  placed  in  a  sand  pot,  with  only 
about  a  pint  of  sand  under  the  bottom  to  distribute  the  weight, — 
for  if  much  sand  be  used  it  is  difficult  to  manage  the  temperature 
nicely.  A  large  Liebig's  condenser  should  be  adapted  to  the 
retort  beak,  and  the  mixture  then  heated  up  as  quickly  as  possi- 
ble to  300°,  when  the  fire  door  is  opened,  and  the  fire  farther 
damped  with  a  layer  of  fresh  coal.  The  temperature,  however, 
goes  on  rising  from  the  heat  of  the  pot  and  sand  till  it  reaches 
about  324°,  where,  by  management  of  the  fire  door  it  may  be 
steadily  maintained  till  the  charge  is  finished.  The  mixture 
becomes  brown  as  it  is  heated  and  boils  at  250°  with  the  distilla- 
tion of  an  ethereal  liquid.  In  proportion  as  sulphurous  acid  gas 
comes  over  with  the  distillate,  the  mixture  becomes  of  a  darker 
color,  and  the  distillate  more  yellow,  but  heavy  oil  of  wine  is  pro- 
duced and  comes  over  with  the  ether  before  the  smell  of  the  gas  is 
noticed.  If  the  temperature  rises  much  above  3S0°  frothing  up  is 
very  liable  to  occur  at  almost  any  stage  of  the  process,  but  if 
maintained,  as  it  can  easily  be,  at  322°  to  326°  half  the  charges, 
at  least,  may  be  finished  without  any  frothing  at  all.  This  termi- 
nation is  very  much  to  be  preferred,  for  the  lifting  of  a  heavy 
frothing  retort  with  such  contents,  at  such  a  temperature  is  at- 
tended with  much  danger.  Each  charge  requires  about  four  hours 
for  its  successful  management ;  and  two  charges  can  be  worked 
off  the  same  retort  in  a  day.  The  discharging  of  so  hot  a  liquid 
is  attended  with  great  risk  of  breaking  the  tubulure,  so  that  it 
