Am.  Jour.  Pharni.  ) 
March,  1910.  J 
Assay  of  Medicinal  Plasters. 
113 
enactment  of  similar  laws  in  the  various  States  has  brought  the 
subject  to  the  attention,  of  the  pharmaceutical  chemist,  and  at  the 
present  time  the  subject  is  one  of  moment  to  both  the  medical  and 
pharmaceutical  professions. 
Prior  to  the  issuance  of  the  last  revision  of  the  Pharmacopoeia, 
no  authoritative  process  of  assay  of  any  medicinal  plaster  appeared 
in  that  work.  In  this  revision  a  process  was  given  for  the  assay 
for  mydriatic  alkaloids  in  belladonna  plasters  made  with  a  rubber 
base.  Those  who  have  given  attention  to  the  subject  will  no  doubt 
agree  with  the  statement  that  has  been  made,  that  it  is  a  very 
difficult  matter  to  assay  some  kinds  of  medicinal  plasters  made  with 
a  rubber  base.  It  is  a  well-known  fact  that  for  some  such  plasters 
no  method  is  known  for  the  assay  of  the  drugs  contained  therein, 
for  the  reason  that  the  drug  used  has  no  alkaloid,  or  no  alkaloid  or 
no  inorganic  substance  capable  of  definite  measurement. 
In  other  varieties  of  these  plasters  the  presence  in  the  rubber  base 
of  resinous  or  other  matters  is  such  as  to  confuse  the  results  and 
make  them  of  doubtful  value.  In  the  laboratory  of  the  writer  con- 
siderable work  has  been  done  in  the  assay  of  this  class  of  prepara- 
tions, and  in  our  work  we  possess  some  advantages  over  any  outside 
laboratory,  in  that  as  the  laboratory  is  connected  with  the  manufac- 
turing department  it  is  at  once  known  exactly  what  has  been  put  into 
a  plaster,  and  it  is  only  necessary  to  provide  methods  of  assay  that 
will  give  the  results  looked  for.  The  methods  and  processes  which 
I  herewith  present  are  simply  those  which  have  been  worked  out  in 
the  laboratory,  more  particularly  as  a  check  to  manufacturing  proc- 
esses. They  are  presented  for  what  they  may  be  worth,  with  the 
hope  that  other  workers  may  have  an  opportunity  to  try  them  and 
thus  bring  out  information  of  value  to  those  interested. 
BELLADONNA  PLASTERS. 
For  belladonna  plasters  we  use  the  assay  method  of  the  eighth  re- 
vision of  the  United  States  Pharmacopoeia.  This  process,  with  some 
slight  modifications,  has  been  entirely  satisfactory  in  our  laboratory, 
where  assays  running  perhaps  into  thousands  have  been  performed. 
It  has  also  had  the  benefit  of  an  extended  check  test,  in  that  in  this 
laboratory  it  is  our  practice  to  first  assay  the  drug  used  in  the 
manufacture  of  the  plaster  and  then  the  solid  extract  made  from  the 
drug;  the  mass  itself  is  made  up  of  the  assayed  extract  taken  in  an 
amount  which  will  give  in  the  finished  product  the  desired  percentage 
