450 
Precipitates  in  Fluid  Extracts. 
fAm.  Jour.  Pharm. 
1       Sept.,  1884. 
chloride  of  sodium.  The  question  that  presents  itself  is,  can  solutions 
of  salts  separate  from  each  other  after  being  mixed  *?  In  continuing 
this  subject,  we  shall  confine  ourselves  to  a  phase  closely  connected 
with  the  foregoing  experiment.  The  experiments  tabulated  herein 
were  made  more  than  a  year  ago.  If  we  had  written  this  paper  before 
passing  to  other  experiments,  doubtless  we  should  have  permitted  our- 
selves to  theorize  more  freely  regarding  the  phenomenon  than  we  care 
to  do  at  present.  As  it  is,  we  shall  present  the  experiments,  and 
endeavor  to  reserve  our  opinions  concerning  them  for  a  future  day. 
It  may  strike  some  persons  that  the  present  paper  is  entirely  ir- 
relevant to  the  subject  of  percolation  and  precipitation ;  but  if  we  are 
permitted  to  complete  this  subject,  we  think  that  it  will  be  shown  that 
it  is  intimately  connected  with  certain  features  that  have  considerably 
troubled  pharmacists  and  others. 
An  unanswered  query,  once  accepted  by  one  of  our  most  prominent 
members,  is  directly  interested,  and  the  phenomenon  presented  herein 
must  be  considered  before  that  query  can  be  satisfactorily  answered. 
A  process  of  percolation,  suggested  once,  in  wThich  the  menstruum 
was  directed  to  be  admitted  at  the  bottom  of  the  percolator,  and  per- 
mitted to  escape  at  the  top,  is  also  concerned. 
Perhaps  the  analytical  chemist  will  find  some  food  for  consideration, 
as  it  does  not  seem  unreasonable  to  suppose  that  the  principle  in- 
volved in  this  paper  may  be  of  practical  value  in  the  separation  of  cer- 
tain bodies  one  from  another.  Then,  too,  it  may  be  found  advisable 
to  forego  the  process  of  filtration,  if  possible,  wrhere  accurate  results  are 
desired.  However,  after  we  have  introduced  the  line  of  experiments, 
and  the  criticisms  into  wrhich  we  have  been  drawn,  these  features  will 
readily  present  themselves  to  those  interested. 
Let  us  now  revert  to  the  separation  of  the  two  salts  by  the  evapora- 
tion of  the  water.  The  explanation  that  naturally  presents  itself  is, 
that  their  separation  resulted  from  the  fact  that  the  chloride  of  sodium 
crystallized,  and  left  a  mother  liquor  of  chloride  of  ammonium.  This 
afterward  evaporated ;  and  thus  the  salts  were  deposited  in  different 
locations.  In  order  to  test  the  correctness  of  the  view,  we  were  led  to 
several  series  of  experiments ;  and  a  section  of  one  of  these  may  be 
illustrated  as  follows.1 
1  We  only  give  enough  of  the  series  to  demonstrate  the  one  feature  to 
which  this  paper  is  devoted.  Our  investigations  have  extended  far  beyond 
the  line  drawn  by  this  report,  but  we  do  not  care  to  impose  upon  the  society 
by  introducing  another  step,  as  it  would  double  the  length  of  the  paper. 
