^ebruary^gis1'  ^       Deodorization  of  the  Cresols.  129 
emulsifiers  in  this  case:  the  presence  of  soap  in  the  solution  causes  a 
milkiness  when  the  compound  is  diluted  with  a  water  which  contains 
calcium  salts.    This  milkiness  is  particularly  undesirable. 
In  view  of  these  facts  it  was  thought  desirable  to  investigate  the 
possibility  of  removing  the  odor  without  decreasing  the  germicidal 
powers  of  cresol.  It  was  found  that  this  is  possible  and  a  process 
is  described  below  by  means  of  which  this  end  may  be  attained. 
Equal  weights  of  cresol  and  concentrated  sulphuric  acid  are 
slowly  mixed  in  an  earthenware  or  glass  vessel  when  considerable 
heat  is  evolved.  Mix  thoroughly  and  heat  at  a  temperature  between 
75  and  no  degrees  C,  preferably  on  a  steam  or  water  bath,  although 
there  is  no  objection  to  direct  heat  providing  the  temperature  is 
kept  within  the  limits  stated.  The  heating  is  continued  until  a  drop 
of  the  liquid  mixed  in  a  test  tube  with  water  shows  only  a  faint 
cloudiness.  If  any  separation  of  oily  drops  occurs  the  heating 
must  be  continued,  unless  it  is  known  that  the  cresol  contains  a 
large  proportion  of  hydrocarbons.  The  length  of  time  necessary 
for  the  completion  of  the  reaction  varies  with  the  quality  of  the 
cresol  taken  but  will  not  exceed  fourteen  hours  and,  with  good 
grades  of  cresol,  is  six  to  seven  hours. 
When  this  stage  is  reached  the  reaction  product  is  to  be  mixed 
with  five  volumes  of  cold  water  and  need  not  be  cooled  before  being 
added  to  the  water.  If  any  oily  matter  separates  it  should  be  re- 
moved. The  diluted  mixture  is  neutralized  with  milk  of  lime  and 
allowed  to  stand  for  twenty- four  hours  to  allow  the  calcium  sulphate 
to  precipitate.  The  clear  liquid  is  decanted  off  and  the  sediment  is 
washed,  the  washings  are  added  to  the  main  portion  of  the  liquid. 
This  is  now  evaporated  to  dryness  on  a  steam  or  water  bath.  Direct 
heat  is  not  permissible,  for  the  compound  burns  easily  with  the  re- 
generation of  the  cresol  odor.  The  dry  residue  is  dissolved  in  a 
little  water  and  tested  for  odor.  If  an  odor  still  persists  it  must  be 
evaporated  again  to  dryness  and  again  tested.  This  procedure  is 
necessary  to  get  rid  of  naphthalenes  and  pyridines,  which  are  fre- 
quently present  in  cheaper  grades  of  cresol  and  which  are  strongly 
odorous.  When  the  residue  shows  no  odor  on  solution  in  water  it 
is  diluted  with  water  to  twice  the  volume  of  the  cresol  originally 
taken  and  the  calcium  is  precipitated  by  sulphuric  acid.  This  must 
be  done  very  carefully  to  avoid  even  the  smallest  excess  of  the  acid 
