344 
Note  on  Dtalyxed  Iron. 
f  Am.  Jour.  Pharm. 
\       July,  1877. 
unless  care  be  taken  to  arrive  at  correct  results.  They  will  retain  their 
clearness  on  boiling,  are  miscible  with  alcohol,  glycerin,  syrup,  etc.v 
but  readily  yield  precipitates  on  the  addition  of  acids  not  in  excess,  or  of 
saline  solutions,  the  precipitates  disappearing  again  on  diluting  with  dis- 
tilled water.  Tannin  added  in  small  quantities,  darkens  the  solution 
somewhat,  and  on  filtering  leaves  but  little  matter  in  the  funnel ;  on 
using  a  stronger  solution  of  tannin  a  well  diffused  gelatinous  precipitate 
takes  place,  having  a  deep  brown,  but  not  a  black  color,  and  the  filtrate 
is  colorless.  Solution  of  nitrate  of  silver  added  in  small  quantity  does 
not  disturb  the  transparency  of  the  liquid  ;  on  adding  more  of  the  former 
a  gelatinous  brown  precipitate  takes  place,  and  the  colorless  filtrate  is  free 
from  iron,  but  the  addition  of  distilled  water  causes  the  precipitate  to 
dissolve  again.  Apparently,  therefore,  the  solution  is  free  from  chloride  ; 
but  on  adding  first  a  slight  excess  of  ammonia,  filtering  from  the  ferric 
hydrate,  acidulating  with  nitric  acid  and  then  testing  with  nitrate  of 
silver,  a  white  precipitate  of  chloride  of  silver  is  formed.  All  these 
reactions  as  well  as  the  slight  astringent,  not  inky  taste,  and  the  intense 
brown-red  color  have  been  observed  by  the  investigators  named  above, 
and  they  characterize  also  the  commercial  products.  A  sample 
recently  handed  to  us,  and  said  to  contain  no,  or  only  traces  of  chlorine^ 
yielded  when  treated  as  above,  abundant  evidence  of  its  presence. 
Physicians  and  pharmacists  should,  therefore,  bear  in  mind  that 
there  is  no  soluble  oxide  of  iron,  but  what  is  sold  as  such,  be  it  imported 
or  made  in  this  country,  is  very  basic  oxy chloride  of  iron.  This  being  the 
case,  the  question  naturally  presents  itself  whether  such  a  solution  can- 
not be  obtained  by  saturating  a  solution  of  ferric  chloride  with  hydrate 
of  iron.  That  question  is  easily  answered  if  the  behavior  to  saline 
solutions  is  taken  into  consideration  and  the  fact  is  remembered  that, 
when  solutions  of  ferric  salts  are  precipitated  by  alkalies  the  ferric 
hydrate  will  invariably  retain  small  quantities  of  the  precipitant,  which 
cannot  be  removed  by  washing  with  water.  These  saline  impurities, 
minute  as  they  may  be,  are  sufficient  to  prevent  the  formation  of  the 
very  basic  oxychloride,  or  if  formed  it  becomes  insoluble  in  the  liquid 
and  nothing  but  dialysis  or  considerable  dilution  with  distilled  water 
can  dissolve  it  again.  To  obtain  it  of  the  maximum  strength  indicated 
by  Graham  (5  per  cent.)  and  also  adopted  by  the  Pharmaceutical  Soci- 
ety of  Paris  (see  page  349),  dialysis  appears  to  be  unavoidable. 
As  to  the  advantage  of  the  dialyzed  over  the  oxychloride  made  by 
