458 
Precipitates  in  Fluid  Extracts. 
Am.  Jour.  riiarm. 
Sept.,  1884. 
We  must  not,  however,  infer  that  this  is  evidence  that  such  a  rule 
will  be  carried  out  with  other  bodies.  Experiments  with  many  salts 
and  other  substances  agreed,  but  some  refused  to  separate,  chloride  of 
sodium  being  carried  to  a  height  of  six  feet. 
We  do  not  design  in  this  paper  to  enter  into  a  theoretical  argument 
regarding  the  causes  for  the  phenomenon  herein  presented.    We  aim 
simply  to  present  the  facts,  and,  in  so  doing,  must  consider  briefly  cer- 
Fig.  vi.  tain  objections  that  have  occurred  to  us 
regarding  the  idea  that  real  solutions  can 
be  separated  from  each  other  by  means  of 
the  capillary  or  surface  attraction  of  ma- 
terials that  have  no  recognized  chemical 
affinity  for  either  of  the  constituents. 
Therefore,  as  the  substances  that  we  have 
named  are  all  solids,  it  might  perhaps  be 
inferred  that  the  molecules  of  these  solids 
are  held  in  the  minute  interstices  of  the 
paper,  while  the  more  mobile  fluid  es- 
capes.1 Such  a  view  could  scarcely  be 
sustained,  because  mixtures  of  liquids  may 
be  separated  from  each  other — indeed, 
even  though  such  a  mixture  is  supposed 
to  have  combined  chemically.  Sulphuric 
acid  and  water  are  accepted  as  having 
rather  an  intense  affinity,  and  their  union 
a,  blotting  paper,   b,  solution  ferric  js  broken  only  by  a  considerable  display  of 
sulphate.    G,  transmitted  liquid.  .  . 
d,  ferric  sulphate  in  paper.  energy.  The  mixture  of  sulphuric  acid  and 
water  is  as  perfectly  disintegrated  by  the  bibulous  paper  as  were  the 
other  substances  named  by  us.  This  can  be  shown  by  making  a  dilute 
solution  of  sulphuric  acid  in  water,  and  allowing  it  to  pass  up  the 
paper,  and  then  pressing  a  piece  of  blue  litmus  paper  upon  the  surface 
of  the  part  of  the  bibulous  paper  that  is  moistened.  The  litmus  will 
change  to  red  for  a  certain  distance,  defined  by  a  line  of  demarkation 
as  distinct  as  that  shown  by  the  iron  salt. 
The  facts,  then,  to  be  presented  in  this  paper  are,  that — 
1st.  Liquids  can  be  separated  from  solids  held  in  solution,  without 
1  It  must  be  admitted  that  such  a  view  is  not  in  accordance  with  our  idea 
of  a  solution. 
