52 
LIQUOR  OPII  COMPOSITUS. 
depurated  solution  of  different  densities,  it  would  seem  only 
proper  to  make  it  up  bj  measure.  But  the  measures  usually 
accessible  are  so  much  less  accurate  than  the  weights  that  they 
cannot  be  relied  on.  Beside,  the  broad  surfaces  of  measures 
are  not  calculated  to  give  that  degree  of  practical  accuracy  re- 
quired now  a  days  in  adjusting  potent  medicinal  agents.  Under 
these  circumstances  measures  and  weights  applicable  to  the  aver- 
age grades  of  opium  will  both  be  given,  even  at  the  expense  of 
complication.  But  the  operator  who  may  have  a  set  of  weights 
which  agree  tolerably  among  themselves  is  advised  to  use  these 
in  preference  to  measures. 
Take  a  tared  flask  marked  in  the  neck  to  hold  17  f§,  or 
510  cc,  (a  common  French  or  German  half  litre  flask  which  is 
marked  Ioav  in  the  neck  answers  well,)  filter  the  opium  solution 
into  it,  and  wash  the  filter  and  residue  through  with  a  little 
water.  To  this  solution  add  1574  grains  or  102  grammes  of 
stronger  alcohol,  and,  having  agitated  the  mixture,  add  water 
until  the  whole  weighs  7870  grains  or  510  grammes.  This 
1574  grains  or  102  grammes  of  alcohol,  measured  at  a  tempera- 
ture of  about  17°  C.  =  62-6°  F.,  measures  4  f^  and  48  rn,,  or 
123  cc,  but  when  this  is  mixed  with  the  watery  solution  there 
is  a  contraction  of  volume  in  the  mixture  equal  to  about  162  n^^, 
or  10  cc,  and  an  increase  of  temperature  of  3  or  4°  C.  =  5*4  or 
7 '2°  F.  When  the  mixture  is  made  up  to  the  7870  grains  or 
510  grammes  it  will  measure  more  than  the  17  f^,  or  510  cc, 
on  account  of  the  rise  of  temperature.  When,  however,  it  is 
cooled  to  the  original  temperature  at  which  the  liquids  were 
when  mixed,  the  measure  will  commonly  be  but  a  small  fraction 
over  or  under  the  measure,  as  the  opium  contains  more  or  less 
extractive  soluble  in  both  water  and  alcohol.  This  7870  grains 
or  510  grammes  of  solution  now  contains  20  per  cent,  of  its 
weight  and  30  per  cent,  of  its  volume  of  the  stronger  alcohol  ; 
and  is  about  the  density  of  water, — that  is  1  cc.  at  17°  C. 
weighs  about  1  gramme.  It  is  perfectly  clear,  and  will  remain 
so  indefinitely,  as  it  contains  alcohol  enough  to  prevent  any 
change  even  in  the  warmest  weather.  It  is  now  ready  for  assay, 
and  should  be  kept  in  a  bottle  to  prevent  loss  by  evaporation 
while  waiting  for  the  result  of  the  assay. 
