LIQUOR  OPII  COMPOSITUS. 
129 
parts  by  measure.  Hence  the  weight  for  morphia,  obtained  by 
the  assay  multiplied  by  79,  gives  the  whole  weight  of  morphia 
in  the  solution ;  and  this  whole  weight  of  morphia  in  the  solution 
divided  by  4,  gives  the  number  of  fluid  parts, — parts  by  measure, 
— or  say,  for  example,  fluid  ounces — of  four  grains  of  morphia 
each  to  which  the  solution  must  be  finally  diluted  in  finishing 
it.  Now,  as  a  fluid  ounce  of  distilled  water  weighs  455  grains, 
(disregarding  the  fractions,)  and  as  a  fluid  ounce  of  the  finished 
solution  weighs  only  450  grains,  it  becomes  necessary  to  multi- 
ply the  number  of  parts  to  which  the  solution  is  to  be  reduced 
or  diluted  in  finishing  by  455,  and  then  to  divide  the  product 
by  450,  to  get  the  number  of  parts  by  weight  to  which  it  must 
be  diluted  in  the  finishing.  Then,  as  12-5  per  cent.,  or  one- 
eighth  of  its  weight,  is  the  proportion  of  Hoffman's  anodyne 
fixed  upon  for  the  constant  quantity,  if  the  last  quotient  or 
whole  number  of  parts  be  divided  by  8,  this  will  of  course  indi- 
cate the  number  of  parts  by  weight  of  Hoffman's  anodyne 
required. 
The  finishing  is  then  simply  the  addition  of  the  12*5  per  cent, 
of  Hoffman's  anodyne,  and  the  making  up  the  weight  with 
water.  The  apparently  rather  complicated  calculation  is  simple 
enough  when  once  understood.  It  is  rendered  necessary  in 
order  that  the  solution  may  be  made  by  weight,  and  be  dis- 
pensed by  measure ;  and  this  dispensing  by  variable  and  incor- 
rect measures  is  then  the  only  source  of  inaccuracy  in  the  prac- 
tice with  it. 
When  the  Hoffman's  anodyne  is  added  to  the  solution,  a  large 
part  of  the  heavy  oil  of  wine  is  precipitated  by  the  abstraction 
of  its  solvents.  By  subsequent  digestion  and  agitation,  how- 
ever, this  appears  to  be  in  great  measure  redissolved  or  com- 
bined, so  that  in  one  experiment  where  many  weeks  were 
allowed  to  the  frequent  shaking,  it  all  disappeared  from  the 
surface  except  just  sufficient  to  form  a  ring  on  the  bottle  at  the 
surface  of  the  liquid.  During  this  digestion  and  shaking  as 
directed  a  small  portion  of  very  light  flocculent  matter  is  pre- 
cipitated, so  that  for  the  removal  of  this  and  the  small  pro- 
portion of  undissolved  oil  the  ultimate  filtration  is  directed,  and 
a  bright,  clear  liquid  is  the  result. 
Each  fluid  ounce  of  this  solution  (weighing  450  grains)  con- 
9 
