AmFe°b"iSarm'}  A  Chemical  Problem.  107 
tint,  and  no  change  in  color  attended  the  passage  of  carbon  dioxide 
through  a  solution  of  borax  and  phenol,  whence  I  concluded  that 
C02  was  in  no  way  answerable  for  the  phenomenon. 
Having  to  a  certain  extent  disposed  of  the  soda  salts,  I  felt  free 
to  introduce  the  chloride  of  ammonium,  and  my  next  step  was  to 
make  a  solution  containing  that  compound,  bicarbonate  of  sodium 
and  phenol.  No  change  was  noticeable  here  for  a  fortnight,  but  at 
the  expiration  of  that  time  a  faint  difference  in  tint  could  be  detected 
and  it  has  gradually  increased  in  intensity.  Meanwhile,  I  was  pur- 
suing my  inquiry,  and  amongst  other  things  I  tried  the  effect  of 
passing  free  ammonia  into  an  aqueous  solution  of  phenol.  Here  I 
observed  the  change  in  color  which  I  was  seeking  ;  the  solution  com- 
menced to  darken  two  days  after  I  fyad  conducted  the  experiment, 
and  behaved  in  a  fashion  corresponding  with  the  development  of 
color  in  the  original  prescription.  I  repeated  the  experiment  and 
kept  the  solution  in  the  dark;  the  only  difference  was  that  the 
coloration  was  slightly  retarded. 
I  had  now  arrived  within  measurable  distance  of  an  explanation 
of  the  phenomenon,  the  coloration  is  caused  by  the  action  of  free 
ammonia  upon  the  phenol. 
The  origin  of  the  ammonia  is  sufficiently  obvious.  We  all  know 
that  it  is  set  free  from  its  salts  by  the  action  of  an  alkali,  and  sodium 
bicarbonate  and  borax,  I  need  hardly  remind  you,  are  both  alka- 
line. 
I  had  not  anticipated  that  ammonia  would  be  more  freely 
developed  by  the  action  of  borax  upon  sal-ammoniac,  than  by  the 
action  of  sodium  bicarbonate  upon  that  salt,  but  the  ammbniacal 
odor  is  much  more  marked,  and  the  action  upon  phenol  is  more 
prompt  in  the  former  than  in  the  latter  case. 
In  conclusion;  I  formulate  the  proposition  that  the  darkening  in 
color  is  due  to  the  action  upon  phenol  of  the  ammonia  liberated 
from  the  ammonium  chloride  by  the  joint  action  of  borax  and  sodium 
carbonate. 
One  word  as  to  the  color.    It  is  not  black.    It  appears  black 
after  long  standing  when  viewed  by  reflected  light,  but  by  trans-- 
mitted  light  the  bluish-purple  tint  is  readily  seen. 
The  mechanical  part  of  these  experiments  was  carried  out  for  me 
by  Mr.  A.  Gunn,  in  the  experimental  laboratory  at  Galen  Works, 
New  Cross. 
