372  Valuation  of  Crude  Carbolic  Acid.  {^k^Zm^' 
cresols,  give  better  results.  A  sample  of  this  kind,  from  which 
3-9  per  cent,  of  water  could  be  separated  by  distillation,  gained 
I- 5  per  cent,  on  shaking  with  salt  solution.  Saturated  with  water,  so 
as  to  contain  12-3  per  cent.,  it  tested  about  8  per  cent.  Similar 
results  were  obtained  with  commercial  "  crude  cresol."  A  satu- 
rated solution  of  calcium  chloride  was  tried  at  the  suggestion  of 
Professor  Coblentz,  but  was  found  to  have  no  advantage  over  the 
solution.  Separation  of  the  liquids  after  agitation  was  also  slower, 
because  of  the  greater  density  of  the  solution.  Distillation  seems 
to  be  the  only  practical  method  of  estimating  water,  and  even 
this  cannot  be  said  to  be  very  exact,  since  the  water  that  distils 
over  contains  considerable  quantities  of  phenol,  and  the  phenol, 
which  comes  over  with  the  water  and  collects  on  the  bottom  of 
the  receiver,  no  doubt  contains  water.  There  is  also  a  small  loss 
of  water  by  vaporization. 
Another  difficulty  lies  in  the  estimation  of  non-phenols  other  than 
water.  In  Allen's  "  Commercial  Organic  Analysis,"  the  following 
method  is  given  for  the  rough  estimation  of  "  tar-oils  ":  "  Place  10 
c.c.  in  a  graduated  tube,  and  gradually  add  20  c.c.  of  a  9  per  cent, 
solution  of  caustic  soda  (free  from  alumina).  Close  and  agitate. 
Neutral  oils  form  a  layer  above  or  below,  after  separating.  To  make 
separation  more  rapid  and  complete,  add  a  known  volume  of  petro- 
leum spirit."  In  applying  this  method  to  three  specimens  of  vary- 
ing composition,  the  writer  was  unsuccessful.  In  each  case  the  mix- 
ture of  acid  and  soda  was  perfectly  clear  and  the  petroleum  spirit, 
though  acquiring  a  dark  color,  did  not  sensibly  increase  in  volume. 
By  extracting  the  alkaline  mixtures  with  ether,  the  samples  yielded 
respectively  about  1,  4  and  5  per  cent,  of  hydrocarbons,  bases,  etc., 
after  spontaneous  evaporation  of  the  ether. 
Muter  and  De  Koningh  [Analyst,  Vol.  12,  p.  191)  estimate  tar- 
oils  by  agitating  20  c.c.  of  the  acid  with  80  c.c.  of  5  per  cent,  caustic 
soda  solution  and  5  to  10  c.c.  of  benzol.  A  dark  layer  which  forms 
under  the  100  c.c.  mark  represents  the  amount  of  tar-oils  in  the 
sample.  This  was  tried  with  two  samples  known  to  contain  at  least 
4  to  5  per  cent,  of  tar-oils,  but  in  neither  case  was  a  dark  layer 
formed  between  the  alkaline  solution  and  the  benzol.  With  one 
sample  the  benzol  increased  in  volume,  but  an  emulsion,  at  the  zone 
of  contact,  which  did  not  break  up  after  twenty-four  hours,  made 
a  reading  impossible.    With  the  other  sample  the  benzol  apparently 
