274  Diffusive  Properties  ^of  Iron.  {^"k^^.^s^so""- 
to  dialyzed  iron  are  really  possessed  by  it,  and  are  likely  to  affect  its 
medicinal  efficacy. 
Dialyzed  iron  has  been  largely  introduced  to  the  notice  of  the  medical 
profession,  and  strongly  recommended  as  an  efficacious  chalybeate, 
which  is  free  from  objections  that  attach  to  other  chalybeate  medicines. 
It  would  appear  to  have  some  strong  recommendations  if  it  could  be 
clearly  shown  that  it  is  capable  of  being  absorbed  during  its  passage 
through  the  intestinal  canal.  But  while  it  is  freely  admitted  that  it  has 
the  advantage  of  being  nearly  tasteless,  free  from  astringency,  and  not 
liable  to  cause  constipation  or  gastric  disturbance,  it  has  at  the  same  time 
been  broadly  asserted  that  it  is  perfectly  inert  on  account  of  its  colloidal 
nature — that  the  oxide  of  iron  is  precipitated  in  the  stomach  in  a  state 
in  which  it  is  insoluble  in  the  acids  of  the  stomach  and  incapable  ot 
undergoing  liquid  diffusion. 
The  following  experiments  were  made  with  a  sample  of  dialyzed 
iron  containing  5-28  per  cent,  of  ferric  oxide  and  '23  per  cent,  of  chlo- 
rine. The  iron  was  completely  precipitated  by  adding  to  the  dialyzed 
iron  twenty  times  its  volume  of  water  of  the  London  water  supply. 
(9,  a.) — The  oxide  of  iron  obtained  from  100  grains  of  the  dialyzed 
iron  by  addition  of  2,000  grains  of  New  River  water  was  collected  on 
a  filter,  washed  with  distilled  water  and  digested  with  water  to  which 
hydrochloric  acid  of  known  strength  was  gradually  added  until  the 
oxide  of  iron  became  apparently  dissolved,  a  clear  and  permanent, 
although  not  brilliant,  reddish-brown  liquid  resulting.  It  was  found 
that  1*44  grains  of  hydrochloric  acid  (HCl)  was  thus  required  for  the 
5'28  grains  of  oxide  of  iron.  This  solution  was  put  into  a  dialyzer, 
but  at  the  end  of  two  days  not  a  trace  of  iron  had  passed  through  the 
septum. 
(9,  b.) — Another  similar  quantity  of  precipitated  oxide  was  digested 
with  double  the  quantity  of  hydrochloric  acid,  namely  2*88  grains  of 
HCl,  but  the  result  at  the  end  of  two  days  was  the  same.  None  of 
the  iron  had  diffused. 
9,  c.) — Another  similar  quantity  of  oxide,  namely,  5*28  grains,  was 
digested  with  7*5  grains  of  hydrochloric  acid  (HCl),  this  being  the 
quantity  required  for  converting  the  ferric  oxide  into  ferric  chloride,. in 
the  event  of  such  conversion  occurring.  In  this  case  it  was  found  that 
after  the  liquid  had  been  in  the  dialyzer  for  two  days  a  very  small 
quantity,  'i  grain,  of  the  iron  had  diffused. 
In  the  last  three  experiments  the  oxide  had  been  digested  at  a  tern- 
