REVIEW  OP  PHARMACOPOEIA  HELVETICA.  211 
distillate  from  two  parts  ferrocyanide  of  potassium  is  collected  in 
eight  parts  alcohol,  and  subsequently  diluted  with  distilled  water  ; 
the  drops  of  this  acid  are,  therefore,  rather  smaller  than  of  our 
preparation. 
iEther  is  purchased  from  chemical  manufactories  and  rectified. 
The  danger  connected  therewith  is  not  as  great  as  to  prepare  it 
in  glass  retorts,  which  our  Pharmacopoeia  directs  and  which  no- 
body follows. 
iEther  aceticus.  Four  parts  exsiccated  acetate  of  soda,  four 
crude  sulphuric  acid  and  three  alcohol,  are  distilled  to  obtain  four 
parts,  which  are  agitated  with  the  same  weight  of  water  and 
sufficient  carbonate  of  magnesia ;  the  ether  is  then  separated  by 
adding  two  parts  chloride  of  sodium,  and  rectified. 
Alcohol  absolutus,  spec.  grav.  81  at  15°  C,  is  scarcely  stronger 
than  our  alcohol  fortius  '817. 
Alumen  ustum.  Five  parts  alum  are  heated  until  three  parts 
remain ;  this  is  not  entirely  exsiccated, — sixteen  to  nine  parts  is 
better,  as  directed  by  the  U.  S.  P. 
Ammonium  chloratum  is  'sal  ammoniac  purified  by  recrys- 
tallization,  with  the  addition  of  ammonia  to  remove  iron.  The 
purified  salt  only  ought  to  be  dispensed  for  internal  use ;  our 
Pharmacopoeia  knows  the  crude  only,  notwithstanding  its  fre- 
quent use  as  an  expectorant. 
Ammonium  chloratum  ferratum  consists  of  twelve  parts  sal 
ammoniac  and  one  crystallized  sesqui-chloride  of  iron,  dissolved 
and  evaporated. 
Aqua  chlori  is  prepared  by  absorbing  the  gas  in  its  passage 
through  several  flasks  half  filled  with  water ;  the  uncondensed 
chlorine  is  passed  into  a  solution  of  protochloride  of  iron  ;  one 
ounce  contains  about  three  grains  chlorine,  and  oxidizes  twenty 
grains  protosulphate  of  iron. 
Argentum  nitricum  is  made  from  pure  silver  and  acid,  the  so- 
lution filtered  through  gun  cotton,  and  the  crystals  heated  in  a 
porcelain  capsule  short  of  fusion,  to  expel  the  excess  of  nitric 
acid.  We  doubt  the  possibility  of  ever  getting  rid  of  all  this  ex- 
cess in  the  directed  way,  because  the  crystals  retain  some  mother 
liquor  mechanically  enclosed,  which  cannot  be  removed  except 
by  fusion.    It  would  have  been  much  better  to  granulate  the 
