Am.  Jour.  Pharm. 
May,  1880. 
Diffusive  Properties  of  Iron, 
269 
or  i8*68  per  cent,  of  the  salt,  and  containing  34*44  per  cent,  of  P'e^Og. 
In  this  case  73'15  per  cent,  of  the  salt  and  70  per  cent,  of  the  iron 
contained  in  the  salt  had  diffused  in  six  days.  The  diffusion  then,  as 
in  the  previous  experiment,  went  on  very  slowly,  and  at  the  end  of 
sixteen  days  it  had  nearly  stopped,  although  the  dialyzer  still  contained 
19*55  grains  of  a  salt  with  52*48  per  cent  of  Fe203  in  it. 
(2,  c.) — A  10  per  cent,  solution  of  a  salt  containing  30*65  per  cent, 
of  FcgOg  was  put  into  the  dialyzer.  In  two  days  the  difFusate  gave 
96*11  grains,  or  48*05  per  cent,  of  the  salt,  and  this  contained  31*42 
per  cent,  of  Yq^O^.  In  four  days  more  another  difFusate  was  obtained, 
which  yielded  27*60  grains,  or  13*8  per  cent,  of  the  salt,  and  contained 
37*46  per  cent,  of  FegOg.  In  this  case  61*85  per  cent,  of  the  salt,.  ^ 
and  66*15  P^^  cent,  of  the  iron  contained  in  the  salt,  had  diffused  in  six 
days.  The  diffusion  had  now  entirely  stopped,  although  there  still 
remained  32*45  grains  of  a  salt  containing  22*55  gf^ins  of  ferric  oxide 
in  the  dialyzer. 
In  the  three  preceding  experiments  the  solutions  used  and  the  diffu- 
sates  obtained  were  neutral  to  test  paper.  The  citrates  employed  were 
apparently  good  commercial  samples,  well  scaled  and  perfectly  soluble,, 
but  they  evidently  differed  in  constitution,  as  indicated  by  difference  in 
the  results  of  their  diffusion,  for  they  were  all  treated  similarly  and 
subjected  to  the  same  conditions.  It  will  especially  be  observed  that 
diffusion  in  the  case  of  (2,  c.)  ceased  entirely  at  the  end  of  six  days, 
although  the  dialyzer  still  contained  32*45  grains  of  a  salt  in  which 
there  were  22*55  grains  of  ferric  oxide,  but  this,  being  in  the  form  of 
a  highly  basic  salt,  was  no  longer  diffusible. 
With  the  view  of  trying  the  effect  of  altered  conditions  on  the  salt 
used  in  the  last  experiment,  a  solution  made  alkaline  with  ammonia 
was  used  as  follows  : 
(2,  d.) — A  10  per  cent,  solution  of  the  citrate  used  in  experiment 
(2,  c.^  was  made  strongly  alkaline  with  ammonia.  In  two  days  the  dif- 
fusate  gave  92*65  grains,  or  46*32  per  cent,  of  a  salt  containing  32*59 
per  cent,  of  Fe203.  Another  diffusate  was  obtained  in  four  days  more 
which  yielded  17*55  grains,  or  8*77  per  cent,  of  salt  containing  51*22 
per  cent,  of  FcoOg.  In  this  case  55*09  per  cent,  of  the  salt,  and  63*93 
per  cent,  of  the  iron  had  diffused  in  six  days.  And  now,  at  the  end  of 
six  days,  diffusion  had  stopped,  as  in  the  previous  experiment,  while 
the  dialyzer  still  contained  an  undiffusible  salt  containing  68*38  per 
cent,  of  Fe203. 
