456 
Precipitates  in  Fluid  Extracts. 
Km.  Jour.  Pharm. 
Sept..  1884. 
Fig.  IV. 
A 
All  of  these  experiments  uphold  the  principle  that  the  weaker  the 
solution  the  quicker  the  separation,  and  the  larger  the  amount  of  the 
escaped  water. 
We  have  mentioned  the  fact  that  mixed  colored  inks  separate  from 
each  other  under  the  influence  of  the  capillary  attraction  of  bibulous 
paper.  It  is  demonstrated  that  certain  salts  will  also  do  this,  and  com- 
pletely. In  order  to  show  that  they  act  independently  of  each  other 
when  dissolved  in  a  single  solvent,  we  call  attention  to  the  following 
experiment : 
Dissolve  separately,  each  in  one  ounce  of  water,  five  grains  of  fer- 
rous sulphate  (and  add  one  drop  of  sulphuric  acid),  five 
grains  of  cupric  sulphate,  and  thirty  minims  of  officinal 
solution  of  tersulphate  of  iron  (ferric  sulphate).  Place 
a  strip  of  bibulous  paper  upright  in  each,  and  it  will  be 
found  that  at  a  certain  height  the  metallic  solution  is  re- 
tarded. This  can  be  readily  shown  by  drawing  a  piece 
of  red  or  yellow  prussiate  of  potash  down  the  paper, 
for  the  characteristic  coloration  will  appear  as  soon  as 
the  reagent  conies  in  contact  with  the  salt.  However, 
it  will  be  found  that  they  separate  at  different  heights 
in  the  papers. 
Now  mix  the  solutions,  and  repeat  the  paper  experi- 
ment. When  the  reagents  are  applied  to  the  paper,  it 
will  be  shown  that  the  ferric  sulphate  extends  only  a 
certain  distance ;  then  a  mixture  of  ferrous  sulphate  and 
cupric  sulphate ;  then  the  ferrous  sulphate  alone ;  and 
finally  a  colorless  solution  passes  onward,  perfectly  free 
from  either  salt.  (Fig.  4 — for  explanation  see  Fig.  5.) 
The  boundary  line  between  each  salt  is  clear  and  sharp. 
Upon  diluting  this  mixture  with  its  bulk  of  water,  the  rule  of  the 
diluted  ferric  sulphate  (Fig.  3)  is  found  to  be  maintained ;  and,  by 
repeated  dilution  of  each  succeeding  solution  with  its  bulk  of  water,  a 
series  of  regular  demarkations  are  obtained,  as  shown  by  Fig.  5. 
In  the  same  manner  solutions  of  certain  alkaloidal  salts  can  be  sepa- 
rated from  each  other,  as,  for  example,  sulphate  of  quinine  and  sul- 
phate of  berberine,  the  quinine  salt  passing  onward  and  leaving  the 
b3rberine.L 
1  It  is  not  unreasonable  to  suppose  that  advantage  may  be  taken  of  this 
principle  to  separate  certain  bodies  that  seem  to  dissolve  and  precipitate 
alike.  Indeed,  we  have  used  it  in  separating  micrystallizable  coloring 
matters  from  crystals  of  organic  bodies,  where  simply  the  close  wrapping 
of  two  or  three  layers  of  blotting  paper  over  the  moist  magma  will  remove 
the  colorinp;  material  as  the  mass  dries  out. 
