12 
ASSAY  OF  ALKALOIDS. 
assaying  alkaloids  cannot  be  correct  because  of  this  statement. 
As  support  for  this  belief  of  his,  he  gives  no  experiment  nor 
proof  whatever,  but  his  individual  opinion,  that  "  he  could  not 
see  any  reason  why  any  mercury  should  necessarily  remain  in 
solution  unless  an  excess  of  iodohydrargyrate  had  been  added, 
or  the  resulting  alkaline  compound  was  to  some  extent  soluble, 
(meaning  as  such)."  "Whether,"  he  continues,  "we  have  com- 
pounds of  one  equivalent  of  Alk.  HI,  and  one  or  more  eq.  of 
Hgl,  an  equation  can  be  formed  to  meet  the  case,  leaving  no 
uncombined  mercury  in  solution." 
For  the  purpose  of  proving  this  against  him  it  is  necessary  to 
introduce  the  record  of  his  assay  with  quinia  and  cinchonia. 
I.  Quinia  requires,  according  to 
Mr.  Groves'  theory.  His  results  show,         My  results  are,        My  theory  requires. 
Chi-fHI-f-2HgI  2Chi+  3HI+6HgI 
100.         140  and  over.  148  to  151.  150  grains. 
His  experiments,  it  seems,  were  made  at  night,  at  the  sea- 
sonable hour  of  9  P.  M.  "  After  130  grain  measures  had  been 
added  the  filtrate  reacted  still  with  iodohydrargyrate,  (N.  B., 
because  there  was  still  some  quinia  in  solution),  but  not  with 
quinia,  (N.  B.,  because  there  was  not  then  any  mercury  in  ex- 
cess) ;  but  with  140  it  reacted  decidedly  with  both  reagents ; 
at  9.30  P.  M.,  half  an  hour  after,  the  same  liquid  reacted  de- 
cidedly with  quinia,  but  scarcely  perceptibly  with  iodohydrargy- 
rate." This  last  deportment  is  what  proved  a  stumbling  block 
to  Mr.  Groves'  perception,  and  he  concludes  not  only  that  my 
numbers  are  incorrect,  but  also  that  the  alkaloid-compound  itself 
passes  into  solution. 
My  own  observation  of  what  passes  at  the  end  of  this  reaction 
differs,  probably  because  it  was  made  in  day-light.  The  reagent, 
which  in  my  hands  is  always  five  times  as  strong,  when  added 
to  the  amount  of  5J  eq.  of  mercury  produces  a  canary-colored, 
flocculent  precipitate,  which  settles  very  rapidly  and  leaves  a 
cloudy  liquid  above  it ;  when  this  is  now  filtered  on  a  watch- 
glass,  every  drop  of  fresh  test  liquor  will  produce  a  white,  crys- 
talline precipitate,  which  continues  exactly  up  to  the  point  of 
saturation,  i.  e.,  of  6  equivalents  of  mercury.  This  is  still 
better  observed  at  the  end  in  the  glass  vessel  containing  the 
