Am,  Jour.  I'barm.  ) 
September.^iyil.  J 
Queries  on  Alkaloidal  Assay. 
425 
SOME  QUERIES  ON  ALKALOIDAL  ASSAY. 
By  W.  a.  Pearson,  Philadelphia. 
Much  good  work  has  been  recently  presented  on  alkaloidal 
assay,  and  it  is  reasonable  to  expect  that  much  more  satisfactory 
and  accurate  methods  will  be  inserted  in  the  next  Pharmacopoeia 
of  the  United  States. 
There  are  a  few  differences  of  opinion  in  regard  to  technic, 
however,  that  should  be  agreed  upon  before  uniformity  is  to  be 
expected. 
Amount  of  Moisture  in  Drug. — Crude  drugs  are  not  as  a  rule 
assayed  in  the  exact  condition  in  which  they  are  received.  Fre- 
quently they  must  be  dried  before  they  can  be  ground  and  this  loss 
of  water  may  amount  to  as  much  as  30  per  cent.  Is  it  advisable 
to  compute  the  results  obtained  to  correspond  to  the  original  con- 
dition of  the  drug  or  to  the  moisture  free  basis? 
Fineness  of  Powder. — It  is  well  known  that  when  a  powder  is 
ground^  all  of  the  particles  are  not  of  equal  size  and  that  if  all  the 
drug  is  ground  and  only  the  particles  of  a  certain  size  are  taken 
the  sample  will  not  be  a  representative  one. 
Would  it  therefore  be  advisable  instead  of  stating  that  the 
powder  should  be  of  a  certain  fineness  to  state  that  it  should  be 
at  least  of  a  certain  fineness  or  between  certain  limits  of  fineness? 
Temperature. — In  certain  alkaloidal  determinations  the  tem- 
perature plays  an  important  part,  in  the  results  obtained.  For 
example,  in  the  assay  of  opium,  the  crystallization  flask  is  directed 
to  be  set  aside  in  a  moderately  cool  place.  No  limits  are  given  in 
U.  S.  P.  for  moderately  cool  "  and  this  temperature  has  been 
variously  interpreted  by  different  analysts.  It  is  certain  that  much 
larger  crystals  are  obtained  near  0°  C.  than  at  slightly  higher 
temperatures ;  it  therefore  seems  important  to  ask  what  influence 
does  temperature  have  upon  the  results  of  an  alkaloidal  assay? 
Fumes. — Free  alkaloids  very  readily  combine  with  acids,  and 
the  analytical  laboratory  usually  contains  fumes  of  hydrochloric 
or  nitric  acids.  Before  the  delicate  titration  of  an  alkaloidal  residue 
is  made  there  seems  to  be  danger  of  these  fumes  combining  with 
the  alkaloid  and  lowering  the  results.  To  what  extent  do  the 
fumes  ordinarily  present  in  the  laboratory  influence  the  results  of 
an  alkaloidal  assay? 
Indicators. — It  has  been  claimed  by  the  analysts  in  one  lab- 
