584  Commercial  Carbolic  Compounds.  {Am'l™T;m7avm' 
the  tube  to  a  convenient  extent.  [These  tubes  are  to  be  procured  from 
Mr.  Cetti  of  Brooke  street,  Holborn,  who  knows  them  as  "  Muter' s 
carbolimeters,"  and  the  entire  apparatus  costs  8s.  6d.]  Before  pro- 
ceeding to  use  the  tube  for  the  first  time,  it  is  necessary  to  find  the 
allowance  to  be  made  for  the  rod.  This  is  done  by  filling  the  tube 
with  brine  up  to  the  75  cc.  mark  and  then  pouring  in  liquefied  carbolic 
acid  up  to  the  85  cc.  mark.  The  rod  is  now  introduced  and  the 
amount  of  displacement  it  causes  noted,  so  that  an  equivalent  allow- 
ance may  be  made  on  ail  future  experiments. 
The  measuring  tube  having  been  charged,  as  already  described,  we 
now  proceed  to  add  very  cautiously,  and  with  constant  stirring  25  cc. 
of  strong  hydrochloric  acid,  and  when  that  is  all  in,  we  follow  it  with 
a  teaspoonful  of  common  salt.  All  the  phenols  now  rise  to  the  sur- 
face, and  when  the  whole  is  at  the  temperature  of  60°F.,  the  volume 
is  read  off,  which  gives  the  amount  of  commercial  carbolic  acid  present 
in  the  75  grammes  of  powder.  If  a  perfectly  acurate  result  be  re- 
quired, it  is  necessary  to  remove  some  of  the  floating  acid  with  a 
pipette,  take  its  specific  gravity,  and  correct  the  volume  reading  to 
weight. 
(2)  MODIFICATION  OF   THE  ABOVE  PROCESS  FOR  USE   WITH  POW- 
DERS ON  A  LIME  BASE,  WHERE  THE  ACIDS  ARE  COMBINED. 
Before  proceeding  with  the  spirit  extraction,  the  weighed  portion  of 
the  powder  is  to  be  treated  in  a  capacious  mortar  with  successive  small 
quantities  of  diluted  sulphuric  acid  (one  in  three)  until  the  whole  mass 
has  a  faintly  acid  reaction,  and  then  the.  process  applied  as  above  de- 
scribed. It  is  necessary  to  be  very  particular  about  the  treatment  in 
the  mortar,  because,  if  the  least  particle  of  the  powder  escapes  the 
action  of  the  acid,  the  results  are  vitiated,  while  at  the  same  time,  any 
marked  excess  of  acid  should  be  avoided.  Both  pestle  and  spatula 
must  be  thoroughly  used. 
(3)  EXAMINATION  OF  A  SAMPLE  OF  COMMERCIAL  CARBOLIC  ACID. 
Case  1 .  The  sample  is  dark  in  color. — Put  some  of  the  sample  into 
the  "  carbolimeter"  up  to  the  20  cc.  mark,  then  gently  add  5  per 
cent,  solution  of  sodium  hydrate  up  to  the  100  cc.  mark,  and  lastly 
add  10  cc.  of  benzol.  Put  in  the  stopper,  and  having  inverted  the 
tube  once  or  twice,  plunge  it  into  cold  water.  Repeat  this  shaking 
and  cooling  until  the  separation  is  complete.  Read  off  the  volume  of 
the  dark  layer,  which  will  now  have  formed  beneath  the  100  cc.  mark, 
