Am.  Jour.  Pharm.  ) 
February,  1909.  j 
The  Assay  of  Drugs. 
63 
The  methods  start  with  the  assumption  that  the  analyst  has  a 
representative  sample  of  the  powdered  air-dry  drug.  Air-dry  drugs 
vary  among  themselves,  and  are  affected  by  atmospheric  conditions 
of  humidity  with  respect  to  the  amount  of  moisture  they  contain. 
Therefore  it  would  be  better  to  make  a  separate  determination  of 
loss  of  moisture  on  drying  and  compute  the  assay  to  a  basis  of  dry 
drug.  A  representative  sample  of  a  crude  drug  is  often  very  diffi- 
cult to  obtain.  If  a  bale  is  ground  and  the  powder  mixed  it  is  easy, 
but  to  make  a  representative  mixture  of  portions  from  different 
places  in  the  package  of  leaves,  roots,  etc.,  requires  trained  judgment. 
There  is  also  difficulty  in  obtaining  proper  comminution  of  small 
samples  of  tough  and  refractory  drugs,  as  every  particle  must  be 
powdered  and  small  mills  do  not  readily  accomplish  this.  For 
example,  one  would  not  obtain  a  representative  sample  of  ipecac  if 
he  rejected  any  of  the  woody  fibre  which  the  mill  refuses  to  grind. 
It  is  important  that  the  powder  be  as  fine  as  the  Pharmacopoeia  di- 
rects for  assay  purposes,  as  extraction  may  otherwise  be  imperfect 
and  cause  variation  in  results. 
In  extracting  the  drug  both  by  the  total  extraction  and  aliquot 
methods,  the  powder  is  directed  to  be  digested  in  a  stoppered  flask 
with  a  certain  amount  of  volatile  solvent  to  which  ammonia  is  usually 
added  to  liberate  the  alkaloid.  The  digestion  is  to  be  accompanied 
with  agitation,  the  amount  of  which  is  somewhat  indefinitely  stated, 
though  in  some  cases  the  use  of  a  mechanical  agitator  is  alternatively 
directed.  The  direction  "with  frequent  shaking"  will  be  inter- 
preted differently  by  different  persons,  and  for  the  sake  of  uniformity 
it  would  be  better  to  direct  "  with  continuous  agitation."  A  me- 
chanical agitator  driven  by  a  small  electric  or  water  motor  is  easily 
arranged. 
The  total  extraction  and  aliquot  methods  are  both  recognized  in 
the  Pharmacopoeia,  the  latter  usually  being  preferred  for  drugs 
which  contain  much  alkaloid  or  are  difficult  to  exhaust.  Both  have 
their  advocates  and  advantages,  but  the  cooperative  work  has  not 
yet  disclosed  a  decided  superiority  on  the  whole  for  either.  A  few 
modifications  are  desirable,  such  as  the  use  of  more  solvent  men- 
struum in  the  total  extraction  of  certain  drugs,  and  filtering  the 
solution  through  cotton  previous  to,  during,  or  after  the  shaking 
out  process. 
A  number  of  alkaloids  after  isolation  from  the  corresponding 
drugs  are  directed  to  be  determined  by  titration.    They  are  dissolved 
