140 
REMARKS  ON  SOME  CHEMICAL  PROCESSES. 
the  commercial  article.  As  the  addition  of  a  small  quantity  of 
sulphuric  acid  to  a  solution  of  salt  prevents  its  decomposition,, 
caused  by  the  formation  of  a  basic  ferruginous  salt,  I  concluded 
to  try  the  effect  of  a  little  sulphuric  acid,  and  met  with  per- 
fect success.  By  the  addition  of  1  fl.  oz.  sulphuric  acid  to  1  gall, 
liquor  ferri  tersulphat.,  I  obtained  crystals  of  a  beautiful  violet 
tinge  and  perfect  form.  These  were  simply  drained  thoroughly 
and  immediately  bottled.  I  have  been  so  far  unable  to  obtain 
the  salt  perfectly  dry  without  injuring  its  appearance.  The 
mother  liquors  will  yield  another  cup  of  crystals  if  evaporated 
gently  and  filtered.  If  the  solution  is  not  filtered  the  salt  will 
have  a  rusty  appearance  from  the  decomposition  of  a  portion  of 
the  salt.  When  large  quantities  are  made  it  is  better  to  use  the 
mother  liquors  with  a  new  portion  of  materials. 
Tinct.  Clilor.  Iron.  When  the  Pharmacopoeia  direction  is 
strictly  followed  in  making  the  solution  of  sesqui-chloride  of 
iron  for  this  tincture,  there  is  danger  of  the  liquid  frothing  over 
towards  the  completion  of  the  process,  unless  the  capacity  of 
the  dish  is  very  much  larger  than  the  bulk  of  its  contents.  By 
long-continued  heat  a  portion  of  the  muriatic  acid,  present  in 
the  preparation  before  the  oxidation  is  completed,  is  also  wasted 
and  frequently  sufficient  to  cause  a  basic  chloride  to  be  formed, 
which,  when  mixed  with  the  alcohol,  is  deposited,  sometimes  im- 
mediately, sometimes  after  the  lapse  of  a  few  weeks.  This  has 
happened  to  me  on  several  occasions,  and  others  have  had  simi- 
lar experience.  For  several  years  I  have  pursued  the  following 
manipulation  in  its  manufacture,  and  have  met  with  invariably 
satisfactory  results.  The  materials  and  relative  proportions 
used  are  the  same  as  in  the  officinal  process : 
Make  the  solution  of  proto-chloride  of  iron  according  to  the 
officinal  directions  and  filter.  Heat  it  to  the  boiling  point,  add 
the  reserved  portion  of  muriatic  acid,  and  take  immediately  from 
the  sand-bath.  Into  another  vessel  (capable  of  holding  one-half 
more  than  the  solution  will  measure  when  completed),  pour  three- 
fourths  of  the  nitric  acid  required.  Place  the  vessel  in  the 
sand-bath  from  which  the  solution  of  chloride  of  iron  has  been 
removed,  and  add  the  latter  in  small  portions  as  long  as  effer- 
vescence is  produced.    If  effervescence  should  cease  before  all 
