272 
Diffusive  Properties  of  Iron. 
Am.  Jour.  Pharm. 
May,  1880. 
a  constituent  of  the  salts.  It  also  appears,  on  comparing  the  results  of 
experiments  (3,  a)  and  (3,  z^'),  that  the  salt  containing  the  larger  propor- 
tion of  oxide  of  iron  diffuses  more  slowly  than  the  other,  and  that  the 
diffusate  contains  a  smaller  proportion  of  iron. 
4.  Citrate  of  Iron  and  ^uinia. — This  preparation,  for  which,  in  its 
most  approved  form,  an  available  process  was  first  published  in  the 
present  edition  of  the  British  Pharmacopoeia,  although  a  somewhat 
indefinite,  or  at  least  an  undefined,  compound,  is  an  important  and  val- 
uable medicine,  and  it  seemed  desirable,  in  connection  with  the  present 
object  of  this  inquiry,  to  determine  the  extent  to  which  it  is  capable  of 
undergoing  diffusion  through  a  membiane. 
A  10  per  cent,  solution,  containing  200  grains  of  a  good  sample  of 
citrate  of  iron  and  quinia,  gave  a  diffusate  in  two  days  yielding  76*8^ 
grains  of  dry  residue,  containing  21*65  per  cent,  of  ferric  oxide.  In 
two  days  more  it  gave  a  further  diffusate,  yielding  2i'i8  grains  of  dry 
residue  containing  28*8  per  cent,  of  ferric  oxide  j  and  again,  in  two 
days  more  it  gave  i6'6  grains  of  a  residue  with  27*7  per  cent,  of  oxide, 
making  the  salt  difi'used  in  six  days  equal  to  57'29  per  cent,  of  that  put 
into  the  dialyzer.  The  proportion  of  quinia  in  relation  to  the  iron 
was  not  determined  in  this  case,  and  in  this  and  other  respects  further 
experiments  have  yet  to  be  made  ;  but  it  is  evident  from  the  results 
obtained  that  citrate  of  iron  and  quinia  is  a  freely  diffusible  prepara- 
tion. 
5.  Sulphate  of  Iron^  Ferrous  Sulphate^  FeS04.7H20. — A  10  per  cent, 
solution  (200  grains  in  2,000  grains  of  solution)  slightly  acidulated  with 
sulphuric  acid  and  dialyzed  for  two  days  gave  a  diffusate  yielding  36'4. 
grains  of  ferric  oxide,  and  dialyzed  for  four  days  more  it  gave  a  further 
diffusate  yielding  14-7  grains  of  ferric  oxide,  thus  making  the  amount 
of  iron,  reckoned  as  ferric  oxide,  diffused  in  six  days,  51*1  grains,  cor- 
responding to  35'7  grains  of  iron,  and  as  the  salt  put  into  the  dialyzer 
contained  40*2  grains  of  iron,  it  follows  that  89*2  per  cent,  of  the  iron 
had  diffused  in  six  days. 
The  experiment  was  carried  on  for  two  days  longer,  in  which  time 
a  further  diffusate  yielding  3*76  grains  of  ferric  oxide  was  obtained, 
making  the  total  amount  of  iron  diffused  in  eight  days  equallto  96  per 
cent,  of  the  whole. 
6.  Persulphate  of  Iron ^  Ferric  Sulphate.— A  solution  was  made  by  dis- 
solving 200  grains  of  ferrous  sulphate,  converting  it  into  the  ferric  salt,, 
and  making  it  up  to  2,000  grains.    The  solution,  therefore,  contained 
