Amj{^r;8p7^rnu}         Tests  for  Carbolic  Acid,  etc.  29 
portions  being  rejected.    The  cresylic  acid  thus  obtained  boiled  chiefly 
at  about  I97°C,  but  another  smaller  fraction  boiled  at  203°C. 
I  believe  this  diffeKence  is  due  to  the  presence  of  two  isomeric  cres- 
ols  in  coal-tar,  having  slightly  different  boiling  points.  Many  of  the 
experiments  were  made  separately  on  both  fractions,  but  without  the 
least  further  difference  in  their  properties  becoming  apparent.  The 
distillations  were  conducted  in  an  atmosphere  of  coal  gas. 
The  Creasote  was  a  sample  of  Morson's  wood-tar  creasote.  It 
boiled  at  2I7°C,  and  so  probably  consisted  chiefly  of  creasol,  as 
guaiacol  boils  at  200°C.1 
It  was  pointed  out  by  Calvert  many  years  ago  that  carbolic  acici 
formed  a  crystalline  hydrate,  of  the  composition  C6HeO,  H20,  which 
fused  at  I7°C.  This  fact  is  usually  ignored  by  the  bookmakers 
though  well  known  to  carbolic  acid  manufacturers.  This  hydrate 
would  contain  16*07  Per  cent-  °f  water.  When  water  is  gradu- 
ally added  to  carbolic  acid  with  repeated  shaking  the  crystals  become 
liquefied,  and  at  length  a  portion  remains  at  the  surface. 
In  order  to  ascertain  how  much  water  carbolic  would  take  up,  about 
13  grams  of  the  crystallized  acid  were  melted  and  boiled  for  a  minute 
or  two  in  a  small  weighed  test-tube  to  drive  off"  traces  of  water.  After 
cooling  the  whole  was  weighed.  Cold  water  was  then  added  gradually 
with  repeated  shaking  until  about  *2  cc.  remained  as  a  layer  on  the 
surface  of  the  liquefied  acid.  This  was  then  removed  by  cautious  use 
of  wet  blotting  paper,  and  the  residual  carbolic  acid  weighed.  9*190 
grams  were  found  to  have  increased  to  12*527,  which  gives  26*6  per 
cent,  as  the  proportion  of  water  in  the  liquid  acid.  On  repeating  the 
experiment  a  liquid  acid  containing  27*0  per  cent,  of  water  was 
obtained.  This  fact  is  of  importance  as  showing  that  carbolic  acid 
will  take  up  far  more  water  than  is  commonly  supposed.  The  pro- 
portion is  also  of  interest,  as  it  corresponds  pretty  closely  to  the 
formula  C6HeO,  2H20.2 
Hence  the  liquid  acid  may  be  regarded  as  a  definite  hydrate  of 
phenol,  but  the  fact  that  warm  carbolic  acid  will  take  up  a  larger  pro- 
portion of  water  than  the  above,  and  that  the  water  is  entirely  sepa- 
rated by  agitation  with  benzol  is  against  this  supposition. 
On  trying  a  similar  experiment  with  cresylic  acid  I  found  that  the 
According  to  some  observers,  at  2io°C. 
'■'The  theoretical  proportion  of  water  in  this  compound  would  be  27*69  per  cent. 
