LIQUOR  OPII  COMPOSITUS. 
55 
multiply  it  by  16  to  know  how  much  morphia  the  remaining 
sixteen-seventeenths  of  the  solution  contains.  Suppose  the 
morphia  in  the  capsule  to  weigh  11-42  grains  or  0'74  gramme. 
Then  11*42  x  17  =  194-14,  and  the  1543  grains  of  powdered 
opium  taken  contained  194-14  grains  of  morphia.  Then,  as 
1543:  194-14:  :  100:  12-58  =  the  percentage  of  morphia  in 
the  opium.  Or,  it  weighs  0-74  gramme.  Then  0*74  x  17  — 
12-58,  and  the  100  grammes  taken  contained  12*58  grammes  of 
morphia.  Then,  as  100  :  12-58  : :  100  .  12-58  the  percentage 
of  morphia  in  the  powdered  opium.  But  there  is  only  sixteen- 
seventeenths  of  the  solution  remaining,  and  the  other  seven- 
teenth part  in  this  supposed  case  has  given  11-42  grains  or  0*74 
gramme  of  morphia.  Therefore,  this  quantity  multiplied  by  16 
would  give  182-72  grains  or  6-04  grammes  as  the  whole  quantity 
of  morphia  in  the  remainder  of  the  solution. 
This  is  by  no  means  the  only  process  of  assay  well  adapted  to 
this  purpose,  and  perhaps  not  the  best  one.  Any  of  the  ordinary 
morphiometrical  processes  are  good  enough,  and  here,  as  in  most 
chemical  processes,  that  one  is  best  to  which  the  operator  is  best 
educated,  and  with  which  he  has  most  experience.  A  practice 
of  nearly  twenty  years,  growing  out  of  the  old  Staples  process 
for  the  extraction  of  morphia,  has  led  the  writer  to  place  a  good 
deal  of  confidence  in  this  plan ;  and  though  it  does  not  pretend 
to  critical  accuracy,  it  is  doubtful  whether  any  process  that  is 
more  complex,  more  difficult,  or  more  critical,  would  bo  adapted 
to  the  present  condition  of  pharmacy.  Pharmacy  should  not 
pretend  to  be  chemistry,  and  results  in  this  direction  which 
may  be  far  short  of  chemical  accuracy  would  be  an  important 
advance  for  pharmacy.  Simple  and  easy  processes  of  assay  are 
alone  applicable  to  pharmacy,  and  the  practice  of  such  soon  leads 
to  greater  accuracy  in  these  first,  and  then  to  more  accurate  pro- 
cesses. This  process  of  assay  is  easily  applicable  to  powdered 
opium,  and  gives  results  the  accuracy  of  which  is  proportionate 
to  the  dexterity  with  which  it  is  applied.  If  a  parcel  of  pow- 
dered opium  is  to  be  assayed  by  this  process,  it  is  only  necessary 
to  take  10  grammes  =  154-3  grains,  instead  of  100  grammes  = 
1543  grains,  and  then  to  divide  the  whole  detail  as  given  by  10. 
Indeed,  the  whole  detail  given  is  but  the  writer's  process  of  assay 
