226  German  Pharmacopoeia  Requirements.  {^™May^9ii*'"* 
over  sulphuric  acid  for  24  hours.  Introduce  sufficient  of  the  dry 
sample  into  a  capillary  tube  of  i  mm.  diameter  to  form  a  column 
2-3  mm.  high  in  the  bottom  of  the  tube.  Attach  the  tube  so  charged 
to  a  suitable  thermometer  and  immerse  in  a  bath  of  sulphuric  acid 
contained  in  a  test  tube  of  30  mm.  diameter.  Heat  gradually  with 
frequent  stirring.  That  temperature  at  which  the  opaque  mass 
becomes  a  transparent  liquid  and  flows  together  in  transparent 
drops  is  regarded  as  the  melting  point. 
In  the  corresponding  requirements  of  the  new  edition,  im- 
provement is  noted  in  the  following  details : 
1.  Beside  the  same  period  and  method  of  drying,  the  sample 
is  required  to  be  "  finely  divided  " ;  and  as  previously  noted  this 
degree  of  fineness  is  specifically  defined  in  another  paragraph. 
2.  The  column  of  sample  in  the  bottom  of  the  capillary  must 
be  2-3  mm.  high  when     tapped  down." 
3.  The  position  of  the  sample  with  reference  to  the  bulb  of  the 
thermometer  is  definitely  defined. 
4.  A  most  important  improvement,  as  I  see  it,  is  noted  in  the 
matter  of  heating  the  bath — against  no  provision  on  this  detail 
in  the  old  edition,  the  new  edition  provides  that  from  a  point  10° 
below  the  assumed  melting  point,  the  rise  in  temperature  shall  be 
at  the  rate  of  2°  per  minute. 
The  period  and  manner  of  drying  is  the  same  "  when  not  other- 
wise stated,"  and  the  definition  of  melting  point  is  the  same. 
The  most  radical  change  (and  one  which  in  my  opinion  is  a 
step  backward)  is  found  in  the  method  applied.  The  new  method 
requires  apparatus  which  is  a  cross  between  the  Roth  apparatus 
and  the  Graebe  apparatus  without  including  the  specific  advantage 
of  either.  It  consists  of  a  test  tube  15  mm.  in  diameter  and  30 
cm.  long,  containing  sulphuric  acid  to  a  depth  of  5  cm.,  and  ad- 
justed in  the  neck  of  a  round  bottomed  bulb  of  80-100  cc.  capacity 
having  a  neck  about  20  cm.  long,  and  3  cm.  in  diameter,  and  con- 
taining sufficient  sulphuric  acid  to  two-thirds  fill  the  neck  when  the 
test  tube  is  in  place. 
The  most  serious  defect  in  the  new  method,  as  I  see  it,  is  the 
absence  of  stirring,  a  detail  which  I  consider  essential  to  a  well 
controlled  melting  point  determination,  and  which  is  not  easily 
applied  with  such  a  double  bath  apparatus.  In  this  detail,  therefore, 
I  feel  that  the  new  requirements  constitute  a  definite  retrogression 
as  compared  with  the  old. 
