Am.  Jour.  Pharm.  ) 
Nov.,  1877,  j 
Iron  and  its  Constituents. 
535 
is  continually  increasing.  A  sample,  which  I  prepared  according  to 
one  of  the  methods  lately  published  in  this  journal,  gave  on  analysis  : 
Ferric  oxide,  Fe203,  .  .  .  .  4 02  1  4-71 
Ferric  chloride,  Fe^Clg,  .  .  ,  .  o  69  J  per  cent. 
Water,  H20,  .  .  .  .  .  95 '29 
100*00 
(Chlorine  =  0*45  per  cent,  combined  with  0.24  per  cent,  iron  to  form  o  69  per 
cent.  Fe2Cl6.) 
It  possessed  all  the  characteristic  properties  of  the  commercial  article, 
leaving  on  evaporation  in  the  water  bath  5*03  per  cent,  of  hydrated 
ferric  oxychloride.  The  approximate  chemical  formula  derived  from 
the  above  analysis  lets  it  appear  as  an  aqueous  solution  of  Fe2Cl6  + 
i2Fe2Os  or  Fe26036Cl6.  In  order  to  obtain  a  very  basic  oxychloride  I 
consider  it  necessary  to  keep  the  solution  to  be  dialysed,  during  preci- 
pitation, or  addition  of  the  separately  precipitated  and  washed  ferric 
oxyhydrate,  at  as  low  a  temperature  as  possible.  Heating  in  an  open 
vessel,  as  well  as  in  hermetically  sealed  glass  tubes,  under  pressure, 
will  produce  a  precipitate  insoluble  on  subsequent  dialysis. 
In  order  to  test  the  percentage  strength  of  dialysed  iron,  without 
evaporating  a  weighed  quantity  to  dryness  or  determining  ferric  oxide 
and  chlorine  by  weight  or  volumetric  analysis,  I  would  propose  the 
following  colorimetric  method,  which  will  give  quite  satisfactory  results, 
particularly  if  applied  to  products  that  have  been  prepared  by  exactly 
the  same  process.  Having  obtained  a  clear,  tasteless,  dard-red  solution, 
which  will  not  precipitate  on  addition  of  silver  nitrate,1  it  is  removed 
from  the  dialyser,  and  compared  with  a  standard  solution  of  known 
strength,  which  has  been  determined  by  careful  weight  analysis.  The 
modus  operandi  is  as  follows  : 
a.  The  standard  solution  consists  of  10  cc.  of  dialysed  iron  (5  per 
cent.),  diluted  with  distilled  water  of  6o°F,  to  the  volume  of  200  cc. 
Twenty  cc.  of  this  solution  are  then  introduced  into  a  true  cylindrical 
tube  of  50  to  60  cc.  capacity,  graduated  into  o*i  cc.  In  order  to 
make  the 
ft.  Colometric  comparison,  2  cc.  of  the  solution  to  be  tested  are  put 
into  a  similar  tube  of  exactly  the  same  dimensions,  and  diluttd  with 
distilled  water  until  its  shade  is  exactly  the  same  as  that  of  the  stand- 
1  On  addition  of  silver  nitrate  I  have  observed  dichroism  of  said  solution.  It 
appears  turbid  in  the  reflected,  but  perfectly  clear  in  transparent  light. 
