Am.  Jour.  Pharm.  ) 
April,  1910.  j 
The  US.P.  Melting  Points. 
179 
or  pharmacist,  although  of  excellent  and  broad  training,  who  has 
not  given  the  subject  of  melting  points  some  special  consideration 
and  study  might  very  reasonably  ask,  "  What  are  the  facts  which 
call  for  and  justify  such  an  investigation?"  In  answer  I  would 
point  to  the  discrepancies,  sometimes  very  marked,  that  exist  between 
the  values  published  for  the  melting  point  of  the  same  compound,  as 
found  in  various  sources  of  the  chemical  and  pharmaceutical  litera- 
ture. In  striking  illustration  of  this  fact  I  would  submit  data,  col- 
lected from  six  different  pharmacopoeias  and  the  important  sources 
in  the  literature,  upon  the  two  compounds  acetanilide  and  resor- 
cinol :  For  acetanilide  the  six  pharmacopoeias  agree  within  a  range 
of  i°  (113-1140),  but  four  different  sources  in  the  literature  give 
four  different  values  ranging  from  112-1160.  In  the  case  of  resor- 
cinol  the  values  vary  from  109-1190. 
The  wide  variation  in  the  published  melting  point  values  of  these 
two  compounds  is  certainly  too  great  to  conveniently  hide  behind  the 
shield  of  legitimate  "  experimental  error,"  yet  they  are  only  two  of 
many,  more  or  less  similar,  examples  that  might  be  cited. 
In  the  case  of  acetanilide  the  fact  that  all  of  the  pharmacopoeias 
included  in  the  comparison  quote  practically  the  same  values  for 
the  melting  point,  also  for  the  boiling  point,  is  very  striking  but 
might  be  misleading.  The  remarkable  concordance  often  found  in 
the  data  of  different  pharmacopoeias  with  reference  to  a  given 
compound  might  suggest  reliable  values,  but  further  study  and 
comparison  is  apt  to  lead,  first  to  the  suspicion  and  then  to  the  con- 
viction that  it  more  probably  indicates  the  respect  and  confidence 
that  the  builders  or  compilers  of  one  pharmacopoeia  feel  toward 
those  of  another. 
Another  striking  fact,  in  answer  to  the  same  question,  is  the 
protest  of  pharmaceutical  chemists  and  manufacturers  against  the 
melting  point  standard  required  by  the  U.S. P.,  and  the  plea  for 
the  allowance  of  a  varying  margin  of  several  degrees  at  moderately 
high  temperature  above  and  below  that  standard ;  all  of  which  indi- 
cates a  chaotic  condition  with  regard  to  melting  points  that  cer- 
tainly calls  for  a  thorough  investigation.  And  in  view  of  the 
fact  that  the  U.S. P.,  through  the  operation  of  the  Pure  Food  and 
Drugs  Law,  has  become  a  legal  standard,  and  because  of  the  very 
general  use  of  the  melting  point  as  one  of  its  most  important  tests, 
it  would  seem  of  especial  interest  and  importance  to  the  Pharma- 
copoeia and  to  all  who  are  in  any  way  connected  with  it  that  the 
