WEIGHTS  OF  THE  PHARMACOPOEIA. 
101 
cases  where  the  plan  has  been  adopted  in  preference  to  the 
regular  notation,  to  avoid  the  use  of  mixed  quantities.  Thus, 
the  formula  for  "  Fowler's  Solution,"  [Liquor  Potassce  Arsenitis,} 
instead  of  employing  3i.,  gr.  iv.  for  the  ingredients,  calls  for  64 
grs.  each  of  arsenious  acid  and  carbonate  of  potassa.  In  like 
manner,  the  formula  for  Liquor  Arsenici  et  Hydrargyri  Iodidi, 
instead  of  requiring  gr.  xv.,  calls  for  35  grs.  each  of  iodide 
of  arsenic  and  red  iodide  of  mercury.  We  may  add  here  an  ex- 
ample showing  the  character  of  change  which  would  be  ordi- 
narily required.  A  simple  formula  will  suffice,  as  that  of  the 
familiar  "  Dover's  Powder,"  for  instance. 
Pulvis  Ipecacuanhas  et  Opii.  (IT.  S.  P.) 
Take  Ipecacuanha,  in  powder,  -    60  grs. 
Opium,  in  powder,  -  60  » 
Sulphate  of  Potassa        -        -  480  " 
Hub  them  together  into  a  very  fine  powder. 
In  cases  such  as  these,  this  mode  of  writing  would  be  even 
easier  than  the  present  mode ;  and  it  would  have  the  advantage 
of  presenting  all  the  ingredients  in  measures  of  the  same  units, 
thereby  greatly  facilitating  their  comparison  and  computation, 
or  the  estimation  of  their  several  divisions  where  a  given  number 
of  doses  is  contained  in  the  preparation.  There  are,  however, 
some  preparations  of  the  Pharmacopoeia  which  are  not  so 
manageable,  and  which  in  their  present  form  certainly  exhibit 
very  awkward  proportions.  Thus,  in  the  preparation  of  Acetum 
Opii,  (Black  Drop,)  the  quantity  of  opium  is  prescribed  at  ^viii. 
(3840  grs.,  or  1  half  pound,  340  grs.)  for  3  pints  and  4  ounces 
of  the  resulting  solution.  Now,  it  is  not  easy  to  perceive  any 
good  reason  for  such  a  proportion  as  this, — giving  1181^ 
grs.  of  opium  to  each  pint  of  the  preparation.  The  quantity  of 
opium  should  be  instead,  1152  grains  to  the  pint,  (1  eighth-pound, 
277  grs. — a  reduction  of  only  29^  grs.  in  the  pint,)  giving  us 
the  convenient  proportion  of  72  grains  to  the  fluid  ounce,  (in- 
stead of  as  now,  ISllgrs.,)  or  of  9  grains  to  the  fluid  drachm. 
And  the  quantity  directed  by  the  formula  should  be  either  1 
pint,  2  pints,  4  pints,  or  1  gallon.  The  binal  progression  (l,oz., 
2  oz.,  4  oz.,  8  oz.,  1  pint,  2  pints,  &c.)  should  indeed  be  the  law 
