AmMi?ch,  SK™' }  Crude  Carbolic  A  cid.  1 1 9 
mixed  with  950  parts  of  water,  should  not  leave  undissolved  more 
than  five  volumes  or  10  per  cent.  It  is  difficult  to  understand  for 
what  reason  such  an  arbitrary  test  is  required.  Fifty  cc.  of  insoluble 
residue  in  1,000  cc.  of  solution  is  difficult  to  measure  with  accuracy, 
particularly  as  the  acid  often  adheres  in  fine  globules  to  the  sides  of 
the  measure.  This  may  seem  a  small  objection,  yet  it  is  very 
important  when  the  acceptance  or  rejection  of  a  large  lot  of  acid 
depends  on  it. 
A  sample  of  excellent  6o°  crude  carbolic  acid  was  tested  by  the 
method  of  the  Pharmacopoeia,  and  answered  its  requirements,  about 
four  volumes  remaining  undissolved.  Another  portion  of  the  same 
acid  was  then  distilled  to  remove  the  small  amount  of  tarry  matter 
and  about  11  per  cent,  of  water  present.  This  fine  light-colored 
acid  showed  by  the  Pharmacopoeia  test  fifteen  volumes  or  30  per 
cent,  insoluble.  In  other  words,  an  acid  containing  all  the  best 
portions  of  the  first  sample  and  having  1 5  per  cent,  more  value 
as  a  disinfectant  would  not  stand  the  test. 
A  sample  of  distilled  cresylic  acid,  free  from  water,  distilling  to 
Per  Cent. 
190,   12 
195,  •   70 
200,   88 
205,   97 
gave  25  volumes  or  50  per  cent,  insoluble.  It  was  found  necessary 
to  add  75  per  cent,  of  crystal  carbolic  acid  (melting  point,  35 °)  to 
25  per  cent,  of  the  above  cresylic  acid,  before  a  mixture  could  be 
obtained  which  would  give  a  satisfactory  result. 
As  the  Pharmacopoeia  requires  an  acid  for  disinfecting  purposes 
only,  and  not  for  preparing  crystal  acid,  it  is  useless  to  require  such 
a  high  per  cent,  of  phenol,  and  it  would  be  undoubtedly  to  the  pur- 
chaser's interest  to  buy  an  acid  free  from  water.  If  the  idea  is  to 
prevent  the  use  of  the  higher  boiling  phenols,  which  are  very  little 
soluble  in  water,  the  difficulty  could  be  overcome  by  the  following 
requirements  : 
It  should  not  be  soluble  in  less  than  15  parts  water  at  150  C,  and 
the  aqueous  solution  should  not  have  an  alkaline  reaction.  It  should 
dissolve  in  10  per  cent,  caustic  soda  solution,  leaving  not  over  5  per 
cent,  insoluble.  Should  not  show  over  2  per  cent,  water,  and  90  per 
cent,  should  distil  under  225 0  C. 
