Am.  Jour.  Pharni. ) 
July,  1915.  j" 
Disinfection. 
317 
finding  the  dilutions  of  the  sample  which  are  as  efficient  as  certain 
dilutions  of  phenol. 
These  phenols  are  so  called  from  their  resemblance  to  carbolic 
acid  or  phenol  proper,  and  are  more  or  less  closely  allied  to  it  both  in 
composition  and  in  properties.  They  differ,  however,  in  several  im- 
portant characteristics.  With  few  exceptions  they  are  liquid  and  will 
not  crystallize  as  carbolic  acid  does ;  they  are  very  slightly  soluble  in 
water,  and  require  a  solvent  of  some  character  to  bring  them  into  a 
condition  in  which  their  activity  can  be  measured  and  applied ;  they 
are  much  less  poisonous  and  corrosive  than  phenol,  and  are  more 
strongly  germicidal.  Chemically  the  phenols  of  ordinary  coal  tar 
differ  from  carbolic  acid  in  having  one  or  more  organic  radicals  at- 
tached to  the  benzol  ring.  The  graphic  formula  for  benzol  is  theo- 
retically considered  to  be  a  hexagon,  familiarly  known  as  the  benzol 
ring.  Each  angle  of  the  hexagon  is  occupied  by  a  CH  group,  and  on 
this  simple  form  thousands  of  organic  compounds  are  built  up  by 
additions  or  substitution. 
Phenol  and  cresol  or  cresylic  acid  are  shown  below  in  their 
generally  accepted  formulae: 
CH  coh  coh  * 
CH  1      ]  CH  CH  (    \  CH  CH  I       I  CH 
chI    Jc  chL    Jch  chI  Jc-ch3 
CH  CH  CH 
Benzol.  Phenol.  Cresol. 
It  is  possible  by  synthesis  to  prepare  derivatives  still  more  strongly 
germicidal  than  those  occurring  naturally  in  the  coal  tar. 
The  insoluble  character  of  the  phenols  and  of  the  creosote  oil  con- 
taining them  requires  the  use  of  an  agent  to  be  incorporated  with 
these  oils  which  will  allow  the  formation  of  a  homogeneous  solution 
or  emulsion  when  the  product  is  mixed  with  water. 
Because  of  the  different  kinds  of  oils  used  and  the  necessarily 
different  treatments  to  prepare  a  substance  .miscible  with  or  soluble 
in  water,  the  coal-tar  disinfectants  differ  among  themselves.  These 
differences  are  unimportant  except  from  the  viewpoint  of  efficiency, 
and  on  this  basis  the  disinfectants  may  be  classified  into  three  groups  : 
Group  1,  those  with  a  phenol  coefficient  of  about  2  which  are 
soluble  in  soft  water,  to  make  a  clear  solution.  Compound  Solution 
of  Cresols  U.  S.  P.  is  an  example  of  this  group. 
Group  2,  the  ordinary  type  of  coal-tar  disinfectants  with  coeffi- 
cient of  2  to  6  which  emulsify  when  mixed  with  warm,  soft  water. 
