* 
34  Tests  for  Carbolic  Acid,  etc.  {^m']lT^™' 
with  a  solution  of  iodine  in  iodide  of  potassium.  Sulphomolybdic  acid, 
also,  gives  a  blue  color  alike  with  creasote  and  carbolic  acid,  even  when 
the  test  is  applied  to  an  aqueous  solution  of  the  sample. 
From  the  foregoing  details  it  will  be  seen  that  in  various  manners 
carbolic  acid,  cresylic  acid  and  wood-tar  creasote  can  be  readily  distin- 
guished from  each  other.  The  case,  however,  is  very  different  when 
we  have  to  deal  with  a  mixture  of  the  three  substances,  such  as  occurs 
in  the  case  of  a  sample  of  creasote  adulterated  with  crude  carbolic  acid. 
In  such  a  case  many  of  the  tests  are  greatly  reduced  in  value  or  ren- 
dered absolutely  worthless.  As  the  problem  is  to  detect  the  coal-tar 
acids  in  presence  of  wood-creasote,  rather  than  the  reverse,  only  affir- 
mative tests  for  the  former  bodies  are  of  service,  and  in  many  cases 
these  are  seriously  modified  by  the  simultaneous  presence  of  creasote. 
Thus,  as  has  been  pointed  out  bv  Mr.  J.  Williams,  the  ferric  chloride 
test  entirelv  fails  to  detect  the  presence  of  carbolic  acid  in  a  mixture  of 
equal  parts  of  that  substance  and  creasote. 
The  only  marked  differences  I  have  been  able  to  observe  between 
Morson's  creasote  and  a  mixture  of  equal  measures  of  that  liquid  and 
Calvert's  No.  5  carbolic  acid  are  the  following  : 
When  shaken  with  twice  its  bulk  of  9  per  cent,  soda  solution,  pure 
creasote  is  dissolved,  and  remains  in  solution  when  the  solvent  is 
increased  to  three  volumes.  The  mixture  was  insoluble  either  in  two, 
three  or  four  times  its  volume  of  9  per  cent.  soda.  This  anomalous 
result  proved  to  be  due  to  the  presence  of  water,  which  reduced  the 
strength  of  the  soda  solution.  When  the  water  was  previously 
expelled  by  boiling  from  the  mixture  of  crude  carbolic  acid  and  crea- 
sote, solution  took  place  with  three  volumes  of  soda. 
When  shaken  with  ^Price's  glycerin  (sp.  gr.  1*258)  pure  creasote 
remained  undissolved,  though  the  proportion  of  glycerin  was  varied  from 
one  to  three  volumes.  The  mixed  creasote  dissolved  completely  and 
readily  in  an  equal  measure  of  glycerin.  The  liquid  was  not  affected 
by  a  drop  or  two  of  water,  but  a  further  addition  caused  precipitation. 
A  mixture  containing  25  per  cent,  of  creasote,  when  shaken  with  an 
equal  measure  of  glycerin,  was  not  precipitated  by  less  than  i\  vol- 
ume of  water. 
Shaken  with  half  its  volume  of  collodium  (B.  P.),  pure  creasote  dis- 
solved to  a  clear  liquid.  The  mixed  creasote  showed  decided  signs  of 
precipitation  when  the  liquid  was  allowed  to  run  gently  from  one  end 
