LIQUOR  OPII  COMPOSITUS. 
123 
tare  of  opium.  It  has  a  fragrant  ethereal  odor,  but  is  almost 
devoid  of  opium  odor,  and  has  a  bitter  taste.  It  is  acid  to  litmus 
paper,  and  forms  a  copious  precipitate  with  ammonia  and  with 
alkaline  carbonates.  Its  s.  g.  is  -995.  When  slowly  evaporated 
to  one  half  its  volume,  and  subjected  to  the  process  of  assay  by 
which  it  is  adjusted,  it  yields  0-88  per  cent,  of  morphia. 
In  order  to  exhaust  opium  thoroughly  some  little  skill  is  re- 
quired. It  is  best  not  to  work  it  with  the  hands  at  first,  but  by 
simple  stirring  and  keeping  it  loose,  to  favor  more  rapid  disinte- 
gration. It  is  best  to  use  a  large  proportion  of  water  at  first  as 
directed,  because  the  opium  is  thus  far  more  perfectly  exhausted 
by  the  first  maceration,  and  the  succeeding  maceration  rendered 
more  effectual.  By  very  skilful  management  the  object  may 
be  attained  with  less  water.  But  it  is  safer,  and  more  applica- 
ble to  all  degrees  of  dryness  of  the  drug,  to  use  the  full  quantity 
and  manipulation  directed.  The  percolations  upon  a  filter  very 
much  facilitate  the  exhaustion,  and  these  to  be  effective  must  be 
performed  continuously.  That  is,  the  residue  must  not  be 
allowed  to  drain  so  close  as  to  contract  and  become  impacted 
before  the  whole  of  the  water  has  been  poured  on,  for  when  it 
contracts  and  separates  from  the  sides  of  the  filter  the  percolation 
is  very  imperfect.  If  the  residue  be  removed  from  the  filter 
carefully,  and  the  funnel  containing  the  filter  be  covered  with  a 
wet  cloth,  the  same  filter  will  serve  for  the  entire  process.  But 
if  the  filter  be  exposed  to  the  air  and  be  allowed  to  dry,  it 
becomes  almost  impervious,  so  that  a  new  one  is  required  for 
each  maceration.  The  expressing  the  residue  can  only  be  well 
accomplished  by  taking  small  portions  at  a  time,  and  making 
them — not  into  a  round  ball  in  the  cloth — but  into  a  long  mass, 
not  thicker  than  two  fingers,  and  then  wringing  this  strongly  in 
the  cloth.  When  a  press  is  used  the  resinous  matter  and 
coutchouc  are  pressed  into  or  through  the  meshes  of  the  cloth 
so  as  to  render  the  cloth  nearly  impervious,  while  the  liquid  is 
entrapped  within.  No  method  of  expression  ever  tried  by  the 
writer  succeeds  so  well  as  the  somewhat  tedious  and  laborious  one 
indicated. 
The  insoluble  residue  of  this  step  of  the  process,  when  dried 
at  a  moderate  temperature,  varies  between  30  and  35  per  cent, 
in  well  selected  opium. 
