Am.  Jour.  Pharm.l 
August,  1899.  J 
Laboratory  Notes. 
395 
The  low  average  would  indicate  that  the  standard  had  been  placed 
too  high  for  this  drug. 
A  very  material  reduction  in  the  time  of  assay  was  accomplished 
by  titrating  directly  from  the  first  chloroform-ether  residue,  as  in 
the  case  of  nux  vomica.  The  presence  of  so  much  chlorophyl  has 
always  proved  a  hindrance  to  the  successful  performance  of  this 
method,  as  the  end-reaction  is  totally  obscured. 
In  the  process  used  the  first  chloroform-ether  extract  was  evapor- 
ated to  dryness,  and  several  portions  of  ether  were  added  succes- 
sively and  evaporated,  which  removes  all  trace  of  ammonia.  A 
small  amount  of  alcohol  is  added  and  an  excess  of  acid  solution 
is  run  in  from  a  burette,  the  amount  being  carefully  noted.  A 
large  amount  of  water  is  now  added  and,  lastly,  about  10  or  15  c.c. 
of  chloroform  and  the  whole  is  well  stirred.  After  several  minutes' 
standing  it  will  be  found  that  the  heavier  chloroformic  layer  con- 
tains all  of  the  fatty  matter  together  with  the  chlorophyl  and  the 
supernatant  aqueous  liquid  is  practically  colorless.  The  desired 
indicator  may  now  be  added  and  titration  successfully  carried  out. 
Potassium  cyanide,  a  chemical  much  used  in  the  arts,  is  one  of 
the  substances  frequently  giving  the  analyst  trouble  from  the  pres- 
ence of  some  impurity  which  causes  a  darkening  of  the  solution 
when  titrated  with  silver  nitrate  v.  s.,  thus  obscuring  the  end- 
reaction. 
Another  difficulty  encountered  in  reporting  upon  this  substance 
is  due  to  the  presence  of  sodium  cyanide,  which  requires  a  lower 
factor  for  calculating  the  per  cent,  when  titrated,  the  result  being 
that  when  titrated  and  calculated  as  KCN,  more  than  100  per  cent, 
of  that  substance  is  indicated,  exclusive  of  carbonates  and  moistuie, 
which  are  always  present  to  some  extent.  It  is  difficult  to  make 
some  customers  appreciate  the  fact  that,  while  it  is  impossible  for 
it  to  contain  more  than  100  per  cent,  of  KCN,  the  presence  of  the 
sodium  salt  makes  it  equal  to  more  than  its  own  weight  of  KCN  in 
actual  working  value. 
The  following  figures  show  the  range  in  KCN  value  of  this  arti- 
cle, the  commercial  having  a  standard  of  30  per  cent.,  and  the 
U.S.P.  90  per  cent.: 
