Amsepr'i884arm'}         Precipitates  in  Fluid  Extracts.  453 
by  the  fibers  of  the  paper  through  which  the  liquid  passed,  until  finally 
all  the  iron  disappeared.  Upon  the  contrary,  it  seemed  to  be  a  strug- 
gling upward  of  several  liquids;1  and  when  the  so-called  solution 
reaches  a  certain  height,  one  part  of  it  is  attracted  onward  with  greater 
force,  and  frees  itself  from  the  others.  There  appears  to  be  an  unequal 
attractive  force  between  the  fibers  of  the  paper  and  the  substances 
passing  through  them ;  there  seems  to  be  an  unequal  and  independent 
capillary  attraction  between  the  fibers  not  moistened  and  the  liquids  in 
contact  with  them.  These  forces  acting  at  the  same  time,  cause  a 
separation  of  solutions  at  a  certain  distance  from  the  surface  of  the 
liquid ;  and  after  this  separation  is  once  effected,  the  liquid  that  has 
freed  itself  from  the  other,  or  others,  seems  to  pass  freely  through  it, 
or  them,  apparently  drawn  from  above  more  rapidly  than  the  other,  or 
others  can  follow.  Thus,  although  the  lower  part  of  the  paper  is 
saturated  with  mixed  solutions,2  the  liquid  that  has  separated  itself 
seems  to  flow  rapidly  through  the  lower  stratum  and  out  of  the  line  of 
demarkation,  without  a  molecule  of  the  iron  salt  accompanying  it.3 
In  continuing  the  study  of  this  phenomenon,  we  find  that  the  propor- 
tion which  the  iron  salt  bears  to  the  liquid  influences  the  point  at  which 
the  separation  of  the  iron  solution  occurs.  If  the  solution  is  dilute,  the 
separation  takes  place  just  above  the  surface  of  the  liquid  in  the  vessel. 
As  it  increases  in  strength,  the  iron  passes  higher  upon  the  paper,  and 
with  officinal  syrupy  solution  of  tersulphate  of  iron  there  will  be  no 
separation.    (See  Fig.  3.) 
This  fact  leads  to  another  point  in  connection  with  the  subject,  to 
wit:  an  attraction  seemingly  exists  between  the  iron  salt  and  the  water, 
which  is  stronger  in  proportion  to  its  concentration.    Therefore,  as  the 
1  Solution  of  tersulphate  of  iron  contains  other  substances  besides  the  salt 
of  iron.  There  are  free  acids,  and  they  are  not  retained  in  accordance  with 
the  detention  of  the  iron.  The  indications  are  also  that  the  coloration  of 
solution  of  ferric  sulphate  is  due  to  accompanying  oxide  or  oxysulphate  in 
soluble  form,  and  that  true  ferric  sulphate  has  no  red  color. 
2  We  admit  that  the  term  solutions  is  not  in  accordance  with  our  present 
understanding  of  a  solution  of  several  salts  in  one  menstruum.  Authorities 
do  not,  we  think,  view  them  as  distinct  liquids  mixed  together  and  existing 
independently  of  each  other,  but  rather  as  one  solution.  For  the  sake  of 
illustrating  these  experiments,  we  shall  speak  of  a  solution  of  different 
bodies  as  being  an  association  of  separate  solutions,  each  retaining  its 
individuality. 
3  There  is*  a  gradual  and  uniform  upward  motion  of  all  the  liquids,  how- 
ever, although  the  lowest  stratum  in  the  paper  moves  slowest. 
