530 
REVIEW  OF  PHARMACOPOEIA  HELVETICA. 
contain  a  uniform  percentage  of  the  drugs  employed,  is  thereby 
carried  out  merely  approximately ;  for  the  liquid  retained  by 
the  residue,  by  the  press-cloth  and  the  filter,  is  charged  with  the 
soluble  principles,  and  its  quantity  must  necessarily  vary  with 
the  nature  of  the  drug.  Most  of  the  pharmacopoeias  of  the  dif- 
ferent German  States  employ  maceration,  and  after  decantation 
direct  the  residue  to  be  expressed,  and  the  liquid  to  be  filtered, 
and  forbid  to  make  up  the  lost  quantity  by  the  addition  of  more 
menstruum.  '  The  preparations  made  in  this  manner  must  neces- 
sarily be  of  more  uniform  strength,  provided  the  drugs  were 
alike  in  quality  ;  made  according  to  the  'Swiss  pharmacopoeia,  it 
is  only  by  the  utmost  care  and  judicious  manipulation  that  they 
can  be  obtained  of  absolute  uniformity.  It  is  curious  that  in 
Europe  the  process  of  displacement  is  so  rarely  employed,  while 
in  this  country  it  has  been  carried  to  great  perfection.  The  ob- 
jections usually  urged  against  displacement  by  our  transatlantic 
brethren  are  all  removed  if  the  main  points  upon  which  the  suc- 
cess of  the  process  depends  are  carefully  attended  to,  namely, 
uniformity  and  fineness  of  powder,  and  judicious  packing,  so  as 
to  insure  even  and  slow  percolation. 
The  vinegars  of  colchicum,  digitalis  and  squill  are  made  to 
represent  one-tenth  their  weight  of  the  drugs,  dilute  acetic  acid 
being  the  menstruum.  Acetum  rubi  idaei  is  made  from  the  syrup 
with  twice  its  weight  of  dilute  acetic  acid. 
The  formula  for  acetum  aromaticum,  or  four  thieves'  vinegar7 
is  as  follows :  lavender  flowers,  wormwood,  peppermint,  rue, 
sage,  angelica  root,  calamus,  and  zedoary,  of  each  8  parts 
cloves  4  parts,  and  sufficient  vinegar  to  make  750  parts. 
Medicated  waters  are  made  by  distillation  in  the  proportion  of 
1  to  20  (aqua  anisi,  cinnamomi,  foeniculi,  petroselini),  1  to  10 
(aqua  chamomillse,  cinnamomi  spirituosa,  melissse,  menthae  cris- 
pae,  menthae  piperita,  salviae,  Valerianae),  and  1  to  5  (aqua  rosa- 
rum,  sambuci,  tiliae).  Aqua  amygdalarum  and  aqua  laurocerasi 
contain  one  grain  hydrocyanic  acid  in  two  ounces;  both  are 
made  by  distilling  from  the  material  its  own  weight  of  water, 
agitating  with  the  volatile  oil,  and  diluting  the  water  so  that  192 
parts  will  yield  one  part  dry  cyanide  of  silver.  These  directions 
are  more  explicit  than  those  of  the  Prussian  and  other  pharma- 
♦ 
