AmseTp°t"r'I9i18JIn""  )  Melting-Point  of  Atropine  Sulphate.  661 
THE  MELTING-POINT  OF  ATROPINE  SULPHATE.1 
By  H.  Droop  Richmond. 
In  the  British  Pharmacopoeia  the  melting-point  of  atropine  sul- 
phate is  given  as  from  1890  to  1900  C. ;  in  the  United  States  Phar- 
macopoeia it  is  stated  that  it  usually  melts  between  1880  and  191 0 
C,  but  when  anhydrous  and  free  from  hyoscyamine  it  melts  between 
181 0  and  1830  C.  These  statements  are  not  in  accordance  with  the 
fact.  The  melting-point  of  atropine  sulphate  is  accurately  given  by 
Carr  in  Allen's  "  Commercial  Organic  Analysis,"  Vol.  VI,  p.  196, 
where  it  is  stated  that,  when  dried  at  ioo°  C,  it  melts  at  1940  C, 
but  the  presence  of  moisture  considerably  lowers  this  point. 
As  a  matter  of  fact,  the  melting-point  has  been  observed  on 
many  occasions  to  be  even  slightly  above  1940  C. 
In  determining  the  melting-point  of  atropine  sulphate,  it  is  im- 
portant that  the  temperature  of  the  bath  shall  not  be  too  close  to  the 
melting-point  as  atropine  sulphate  takes  up  a  small  quantity  of  water 
very  easily,  and  if  immersed  in  a  bath  only  a  few  degrees  below  the 
melting-point  this  water  is  driven  off  rapidly,  but  before  being  so 
it  causes  the  salt  to  sinter  together  and  acquire  an  appearance  which 
may  be  mistaken  for  melting,  .and  this  will  take  place  within  a  very 
few  degrees  of  the  temperature  of  the  bath.  Shortly  after  this  the 
salt  loses  its  water,  becomes  anhydrous,  and  does  not  actually  melt 
until  the  proper  temperature  has  been  reached ;  a  false  melting-point 
many  degrees  low  may  be  easily  recorded.  If,  however,  the  tem- 
perature of  the  bath  is,  say,  25 0  or  300  C.  below  the  melting-point, 
the  water  is  not  driven  off  so  rapidly,  and  the  sintering-point  is 
passed  without  any  marked  change,  or  anything  which  could  be  mis- 
taken for  the  change  which  takes  place  at  a  true  melting-point. 
The  statement  in  the  United  States  Pharmacopoeia  that  when  anhy- 
drous and  free  from  hyoscyamine  it  melts  between  181 0  and  1830 
C.  appears  to  be  untrue,  and  is  probably  based  on  an  old  statement 
in  a  former  British  Pharmacopoeia. 
1  From  the  Analyst  for  May,  1918. 
