REVIEW  OF  PHARMACOPOEIA  HELVETICA. 
531 
copoeias,  which  distil  a  certain  quantity  of  water,  and  require 
this  to  be  of  a  certain  strength.  The  necessity  for  keeping 
those  two  waters  is  not  very  obvious ;  other  pharmacopoeias 
very  properly  allow  the  dispensation  of  one  for  the  other,  since 
the  prescribed  strength  of  hydrocyanic  acid  in  both  is  alike  ; 
this  identity  is  recognized  in  the  Swiss  pharmacopoeia,  by 
directing  either  of  the  waters  to  be  diluted  with  23  parts  dis- 
tilled water,  to  obtain  aqua  cerasorum. 
Under  the  name  of  aqua  aurantii  the  commercial  triple  orange 
flower  water  is  used,  and  a  rectification  directed  in  case  this 
should  be  contaminated  with  metal.  The  formula  of  our  phar- 
macopoeia, requiring  distillation  from  the  (dried)  flowers,  we  do 
not  believe  is  ever  followed,  on  account  of  greater  cheapness  and 
superior  quality  of  the  proper  commercial  article. 
Our  pharmacopoeia  has  a  better  camphor  water  than  the  aqua 
camphorata  of  the  Swiss,  which  is  made  by  triturating  two  grs. 
of  camphor  and  of  gum  arabic  with  one  ounce  of  water. 
Aqua  chlori  is  obtained  by  passing  chlorine  through  a  series 
of  (Woulfe's)  bottles,  partly  filled  with  distilled  water,  the  unah- 
sorbed  gas  being  conducted  into  a  solution  of  protochloride  of 
iron.  The  water  must  contain  not  less  than  3  grains  chlorine 
in  the  ounce. 
Aqua  rubi  idsei  is  made  from  the  residue  left  on  expressing  the 
juice,  by  macerating  it  in  water  w7ith  a  little  carbonate  of  pot- 
assa  and  distilling  two  parts. 
In  making  aqua  calcarise,  the  burned  lime  is  first  wTashed  by 
decantation  with  50  parts  water,  to  remove  alkalies  and  alkaline 
salts — a  commendable  precaution. 
For  preparing  gun  cotton  the  process  is  similar  to  our  officinal 
one,  except  that  one-half  of  the  sulphuric  acid  used  is  Nordhau- 
sen  acid,  and  the  cotton  is  macerated  three  to  five  minutes.  One 
part  of  it  dissolved  in  18  p.  ether  furnishes  collodium.  Oollodium 
cantharidatum  is  nearly  one-half  stronger  than  the  correspond- 
ing preparation  in  this  country. 
Colocynthis  prseparata  (with  five-sixths  colocynth)  and  cuprum 
aluminatum  (s.  lapis  divinus)  are  made  by  the  well-known  for- 
mulas ;  also  Zittmann's  decoction,  in  which  cinnabar  and  calomel 
