AmNS"r;i?93arm'}       Cause  of  Coloration  of  Phenol.  543 
Under  all  conditions  a  coloration  was  found  to  result,  even  with 
the  fifteen  times  distilled  product,  whilst  comparative  tests  showed 
that  no  further  purification  had  been  effected  after  the  second  distil- 
lation. Ammonia  in  concentrated  solution  produces  a  deep  blue 
coloration,  identical  with  Phipson's  "  phenol  blue,"  and  probably 
the  same  product  as  phenol-quinone-imide.  The  formation  of  this 
color  has  long  been  known,  and  seems  to  have  been  quite  overlooked 
by  Fabini  in  his  statement  that,  in  addition  to  ammonia,  metallic 
salts  and  hydrogen  peroxide  are  also  necessary  for  a  coloration  to 
be  formed.  Very  dilute  ammonia,  in  common  with  hydrogen  per-, 
oxide,  caustic  potash,  hydrogen  peroxide  in  presence  of  ammonia,  or 
of  caustic  alkali,  metals,  or  metallic  salts,  with  or  without  hydrogen 
peroxide,  produces  a  reddish  coloration.  The  intensity  and  tint  of 
the  colors  produced  by  these  different  reagents  vary  considerably, 
but  in  most  instances  it  inclines  to  red — the  color  usually  formed  in 
commercial  phenol.  Whilst  it  is  not  likely  that  these  colors  are 
identical,  it  is  probable  that  they  are  closely  allied  products,  and 
the  conditions  of  their  formation  point  to  their  being  oxidation  pro- 
ducts of  phenol.  Gentle  heating  in  all  cases  aids  the  formation  of 
these  colorations. 
The  phenol,  both  after  nine  and  after  fifteen  distillations,  was 
carefully  tested  for  metallic  impurities  and  was  found  to  be  quite 
free  from  the  same.  Further,  in  order  to  test  whether  iron  and 
copper  salts  were  readily  carried  over  by  phenol  when  distilled,  the 
product  was  distilled  after  the  addition  of  these  metals  and  of  their 
salts,  with  the  result  that  after  two  careful  distillations  from  glass 
vessels  the  distillate  was  found  quite  free  from  metallic  contamina- 
tion. 
That  pure  phenol  behaves  as  described  with  the  above  reagents 
was  confirmed  by  applying  the  same  tests  to  phenol  purified  by  sub- 
limation, and  also  to  that  obtained  by  the  saponification  and  subse- 
quent decomposition  of  gaultheria  oil. 
Of  greater  importance  than  the  action  of  these  various  reagents 
upon  purified  phenol,  is  the  fact  that  the  pure  product  obtained  by 
each  of  the  above  processes  does  of  itself  become  colored  when 
exposed  to  ordinary  moist  air.  The  coloration,  which  gradually 
deepens  from  pale  pink  or  brown  to  red,  is  always  accompanied  by  the 
absorption  of  moisture,  and  the  reddening  is  especially  conspicuous 
in  the  partially  liquefied  parts  of  the  sample.    This  coloration  does 
