OLEUM  iETHEREUM  AND  SPIRITUS  0BTHERIS  COMPOSITUS.  199 
is  better  to  use  two  retorts,  when  three  charges  can  be  convenient- 
ly worked  off  from  one  fire  in  a  day. 
When  a  small  quantity  of  water  is  poured  into  a  frothing  retort 
it  causes  the  distillation  of  a  colorless  watery  liquid  of  a  most 
agreeable  aromatic  odor  and  taste,  quite  different  from  that  of 
oil  of  wine. 
With  these  proportions  the  oily  stratum  of  the  distillate  is 
almost  always  on  top,  because  the  water  that  comes  over  is  highly 
charged  with  sulphurous  acid.  With  the  proportions  of  the 
Pharmacopoeia,  however,  it  is  as  often  below  as  above. 
When  two  or  more  charges  are  worked  off  at  one  making  it  is 
economical  to  collect  the  oily  strata  of  the  distillate  in  a  small 
retort,  and  to  recover  the  ether  from  the  whole  at  a  temperature 
below  140°.  The  oily  residue  is  then  thrown  into  thrice  its 
bulk  of  water  and  well  stirred.  The  oil  separates  at  once  in 
colorless  (or  nearly  so)  opalescent  globules,  and  falls  to  the  bot- 
tom of  the  vessel  nearly  free  from  impurities.  The  precaution- 
ary washing  with  dilute  solution  of  carbonate  of  soda,  and  again 
with  distilled  water  is,  however,  advisable  and  proper.  The 
whole  is  then  thrown  into  a  well  moistened  filter,  from  which, 
when  drained,  it  is  drawn  into  a  measure  through  a  small  hole 
made  in  the  bottom  of  the  filter. 
These  washings  are  wasteful,  and  occasion  the  greater  part  of 
the  loss  in  working  on  the  small  scale,  the  water  being  always 
left  opaque  from  small  particles  of  oil  in  suspension.  In  washing 
5  f.^  of  oil,  about  8  minims  nearly  is  lost  each  time,  or  an  aggre- 
gate of  nearly  half  a  drachm.  From  the  difficulty  with  which  this 
suspended  portion  separates  from  the  washings  upon  longstand- 
ing, and  from  the  fact  that  the  washings  increase  the  s.  g.  of  the 
product  very  much,  it  is  probable  that  the  portion  thus  lost  is 
mainly  light  oil  of  wine  or  etherole. 
When  oil  of  wine  is  made  in  quantity,  and  to  be  kept,  it  should 
be  diluted  with  twice  its  bulk  of  alcohol,  to  protect  it  from  de- 
composition or  change  of  color,  for  without  this  it  becomes  dark 
colored,  and  more  impure  than  before  being  washed ;  but  how 
long  beyond  nine  months  it  will  remain  unchanged  when  thus 
diluted  is  not  yet  determined.  Upon  the  scale  of  this  formula 
the  cost  of  materials,  apparatus  and  fuel,  without  estimating 
labor,  will  not  produce  heavy  oil  of  wine  at  less  than  $1.60  to 
