Am.  Jour.  Pharru.  1 
September,  1899.  / 
Wood-Tar  Creosote. 
411 
It  is  sometimes  very  difficult  to  differentiate  between  the  various 
creosotes.  Especially  is  this  the  case  when  'slight  admixtures  are 
dealt  with.  Qualitatively,  beech  and  oak  creosotes  are  alike.  This 
is  probably  true  of  other  creosotes.  E.  Hirschsohn1  has  compared 
beechwood  tar  with  the  tars  of  birch,  fir  and  juniper.  Apparently 
he  has  established  identity  tests  for  the  several  products  when  un- 
mixed. But  it  is  the  writer's  experience  that  when  mixtures  of  the 
above  substances  are  met  with,  many  uncertainties  present  them- 
selves. 
Distinctive  tests  tor  creosote  itself  are  found  in  books,  but  they 
are  of  little  service  in  practice,  where  positive  results  only  can  be 
relied  on.  For  example,  carbolic  acid,  cresylic  acid  and  creosote  can 
readily  be  distinguished  from  one  another,  but  it  is  quite  a  different 
thing  if  mixtures  of  these  substances  have  to  be  dealt  with.  The 
simultaneous  presence  of  these  substances  seriously  modifies  the 
identity  tests. 
Oak  wood  creosote  is  much  more  caustic  than  beechwood.  This 
is  due  to  the  fact  that  the  former  contains  a  larger  proportion  of  the 
monophenols  and  a  correspondingly  smaller  amount  of  guaiacol  than 
the  latter.  Both  contain  about  the  same  amount  of  creosol  and  its 
homologues.  Pine  wood  creosote  distilling  between  200°  and 
220°  C.  was  found2  to  contain  40  per  cent,  of  monophenols,  20  3 
per  cent,  of  guaiacol  and  37-5  per  cent,  of  creosol  and  its 
homologues. 
There  is  also  some  difference  in  the  specific  gravities  of  the  vari- 
ous creosotes.  The  U.S.P.  requires  a  specific  gravity  not  lower 
than  1070  at  I5°C,  while  the  B.P.  is  more  rigid,  in  that  the 
lowest  limit  cannot  be  below  1-079  at  150  C.  The  former  can  easily 
be  met  with  by  a  creosote  that  does  not  contain  any  guaiacol.  It 
seems  desirable  to  make  this  requirement  slightly  more  rigid. 
From  the  above  statements,  it  can  readily  be  seen  that  the 
analyst  is  liable  to  be  confronted  with  considerable  vagueness  when 
he  attempts  to  identify  the  various  creosotes  and  mixtures  of  the 
same.  But  be  this  as  it  may,  we  are,  nevertheless,  able  to  get  at  the 
quality  of  a  creosote  very  closely  by  careful  examination,  as  the 
data  in  the  table  below  will  show. 
1  1898,  Pharm.  Ztg.f.  RussL,  35,  801. 
2 1894,  Comp.  rend.,  i/g,  1276. 
