Am.  Jour.  Pharm. 
April,  1920. 
Purified  Cresol  {Cresylic  Acid). 
251 
In  the  process  of  evaporating  the  solution  it  was  observed  that 
the  vapors  smelled  distinctly  of  pyridine,  and  further,  that  after  a 
certain  time  no  odor  of  this  character  could  be  detected.  Carrying 
this  experiment  to  its  conclusion  and  recovering  the  cresols,  they 
were  found  to  be  practically  free  from  the  objectionable  odor  of  the 
crude  cresols  and  on  redistillation  a  water-white  soluble  product 
was  obtained  with  no  odor  but  that  of  the  pure  cresols. 
The  practical  working  out  of  this  process  is  as  follows :  Dis- 
solve the  crude  cresol  in  a  solution  of  caustic  soda  molecularly 
equivalent,  using  sufficient  water  to  dilute  the  sodium  cresylate  to 
a  25  per  cent,  solution.  Then  boil,  or  drive  live  steam  through  the 
solution  until  the  odorous  impurities  have  passed  off  with  the  steam. 
If  the  solution  is  boiled  over  an  open  flame,  care  is  necessary  to  avoid 
concentrating  the  solution  too  much,  as  the  cresylate  breaks  up 
and  free  cresol  is  volatilized  and  may  take  fire.  It  is  important  to 
add  water  to  replace  that  lost  by  evaporation. 
The  time  necessary  to  vaporize  the  impurities  varies  with  the 
amount  present,  and  can  be  determined  by  smelling.  "The  nose 
knows"  when  the  pyridine  is  gone.  The  solution  should  be  allowed 
to  become  cold  and  then  observed  to  see  if  naphthalene  or  other 
neutral  oils  are  present.  Any  floating  oil  can  be  skimmed  off,  while 
the  naphthalene,  if  any  remains  un volatilized,  can  be  removed 
by  filtration  or  centrifuging. 
Treatment  with  sulphuric  acid  equivalent  to  the  alkali  originally 
used  will  break  up  the  cresylate  and  set  free  cresol  which  can  be 
recovered  as  a  supernatant  layer  over  the  sodium  sulphate  solution. 
Separation  should  be  very  complete,  as  the  water  otherwise  present 
causes  trouble  in  distilling. 
The  removal  of  these  two  impurities,  which  rarely  amount  to 
more  than  5  per  cent,  of  the  cresols,  is  therefore  equivalent  to  a 
complete  purification  of  the  substance,  since  the  color  is  auto- 
matically removed  by  redistillation,  and  a  careful  observation  of 
the  temperature  of  distillation  at  the  end  of  this  step  insures  the 
removal  of  the  higher  boiling  phenols  which  are  less  soluble  than  the 
cresols  and  may  for  that  reason  be  considered  as  impurities. 
Toxicity  Assay. 
Sample . 
Animal . 
Method 
Purified  cresols 
Guinea  pigs 
Subcutaneously 
