COLOR  TESTS  FOR  STRYCHNIA,  ETC. 
519 
alkaloid  under  examination  sulphuric  acid  in  small  quantity — 
pure,  strong  and  cold ;  and  it  undergoes  no  change  of  color. 
The  alkaloid,  therefore,  whatever  it  may  be,  belongs  to  the  class 
of  which  strychnia  is  one. 
To  this  cold  acid  solution  of  the  alkaloid  we  add  a  minute 
fragment  of  bichromate  of  potash,  ferricyanide  of  potassium, 
permanganate  of  potash,  peroxide  of  lead,  or  peroxide  of  man- 
ganese. The  result  is  the  remarkable  development  of  successive 
transient,  or  short-lived,  colors  already  described. 
The  negative  reaction  of  strong  cold  sulphuric  acid  on  strych- 
nia, followed  by  the  effect  of  heat  on  the  acid  mixture,  and  this 
by  the  peculiar  colors  produced  by  the  application  of  the  color- 
developing  substances  to  the  cold  acid  mixture,  constitute  a 
series  of  phenomena  which  afford  fair  promise  of  proving  the 
means  of  a  successful  diagnosis  of  the  alkaloids. 
To  this  work  of  distinction  I  now  address  myself,  and  in  order 
to  prepare  the  way  more  completely  for  the  work  of  tabular 
analysis  towards  which  the  details  given  in  my  former  com- 
munication have  been  tending,  I  must  again  revert  to  the  ques- 
tion whether  the  action  of  the  color-tests  on  strychnia  is,  or  is 
not,  characteristic,  and  therefore  diagnostic. 
This  is  a  question  which  must  have  suggested  itself  to  every 
chemist  engaged  in  medico-legal  inquiries  as  of  the  utmost  prac- 
tical importance,  and  one  chemist  (Mr.  Thomas  E.  Jenkins) 
having  been  employed  to  investigate  a  case  of  suspected  poison- 
ing, in  which  the  color-tests  gave  indications  of  the  presence  of 
strychnia,  very  properly  put  the  question  to  the  test  of  experi- 
ment by  applying  to  a  variety  of  active  principles,  including 
most  of  the  alkaloids,  first,  colorless  concentrated  sulphuric  acid, 
and  then  a  fragment  of  a  crystal  of  bichromate  of  potash.  The 
experiments,  which  were  carefully  performed,  and  appear  to 
have  been  strictly  comparable  one  with  another,  embraced  no 
less  than  fifty  alkaloids  and  active  principles,  derived  from  the 
animal  as  well  as  the  vegetable  kingdom,  and  among  them  urea 
and  uric  acid,  and  cantharidine.  More  than  half  of  these  sub- 
stances differed  from  strychnia  in  yielding  color  when  treated 
with  sulphuric  acid.  The  smaller  half  resembled  strychnia  in 
this  respect.  But  not  one  of  the  whole  fifty  gave  with  the  bi- 
chromate of  potash  the  characteristic  colored  reactions  of  strych- 
