AN  IMPUEITY  IN  TINCTURE  OF  CHLORIDE  OF  IRON.  109 
bottle  containing  the  tincture.  Just  at  this  point  two  modes  of 
procedure  may  be  adopted.  First,  the  tincture  may  be  decanted 
dear  from  the  crystals,  which  may  be  then  redissolved  in  a  small 
amount  of  boiling  muriatic  acid,  diluted  with  an  equal  measure 
of  alcohol,  filtered  rapidly  while  hot,  and  set  aside  for  crystalli- 
zation ;  or  secondly,  the  tincture  may  be  heated  by  a  water-bath 
to  boiling,  without  removing  the  granular  crystals.  In  this  case 
a  copious  yellowish-brown  precipitate  will  take  place  identical  in 
appearance  with  the  well  known  precipitate  from  tincture  of  iron 
as  made  from  the  subcarbonate.  This  precipitate  may  be  col- 
lected and  dissolved  in  boiling  muriatic  acid  and  alcohol  as  in 
the  first  manner,  and  set  aside  to  cool  and  crystallize.  Three  or 
four  ounces  of  the  acid  and  alcohol  will  probably  dissolve  the 
greater  part  of  the  precipitate,  but  if  much  has  formed  it  will 
take  proportionally  more.  After  crystallization  has  taken  place 
they  must  be  collected  on  a  filter  of  white  paper,  and  washed 
with  a  little  diluted  alcohol  and  rinsed  with  distilled  water,  when 
they  may  be  dried  in  any  convenient  way. 
The  crystals  may  be  made  by  the  above  recipe,  omitting  the 
subcarbonate  of  iron  and  acting  on  the  glass  alone,  and  proceed- 
ing exactly  in  the  same  way. 
Having  detailed  the  process  of  obtaining  the  above  substance,  . 
a  few  remarks  upon  its  properties  will  not  be  amiss. 
There  seem  to  be  at  least  three  modifications  of  it,  or  perhaps 
three  difierent  combinations  of  it  with  other  substances. 
First.  The  granular  state, — the  result  of  its  primary  crystalli- 
zation from  the  fresh  hot  tincture  after  several  days.  (They 
begin  to  form  as  soon  as  the  tincture  cools.) 
Second.  The  yellowish-brown  precipitate  obtained  by  boiling 
the  tincture  in  contact  with  the  first  or  granular  crystals.  This 
seems  to  be  the  same  precipitate  so  often  noticed  in  the  tincture 
of  iron.  The  action  of  the  heat,  and  perhaps  etherification,  ap- 
pears to  accomplish  in  a  few  minutes  what  ordinarily  takes  weeks 
and  months  to  do  the  same. 
Third.  The  white,  silky  crystals,  the  most  remarkable  of  all 
its  forms,  and  about  which  the  whole  of  this  has  been  written. 
These  crystals  may  be  heated  to  dull  redness,  with  but  little 
change. 
