522 
COLOR  TESTS  FOR  STRYCHNIA,  ETC. 
tests,  was  obviously  well  adapted  to  this  purpose.  It  has  the 
effect  of  dissolving  the  alkaloids  and  active  principles  without 
change  of  color  in  the  case  of  one  considerable  group  (Table  1.) 
and  ivith  change  of  color  in  the  case  of  another  considerable 
group  (Table  11.)  The  first  group  (Table  I.)  comprises  the 
majority  of  the  active  poisonous  principles — strychnia,  brucia, 
morphia ;  atropia,  picrotoxia,  aconitina  ;  and  the  animal  prin- 
ciple cantharidine.  With  these  and  several  other  alkaloids  and 
active  principles,  some  of  which  are  very  harmless  ones,  con- 
centrated sulphuric  acid  either  produces  no  change  of  color,  or 
a  faint  yellow,^  straw,  or  buff  tint.*  I  speak  of  cold  concentrated 
sulphuric  acid,  applied  as  in  the  preliminary  to  the  color-tests 
for  strychnia. 
The  next  object  which  I  had  in  view  was  to  subdivide  these 
two  large  groups  (Tables  I.  and  11.)  each  into  two  or  more 
smaller  groups  by  some  second  test,  which  might  also,  perchance, 
produce  in  some  members  of  the  two  groups  characteristic  reac- 
tions, so  as  to  eliminate  or  separate  them  at  once.  For  this 
purpose  I  tried  the  effect  of  warming  the  acid  solution  of  the 
alkaloids  by  passing  the  porcelain  slab  through  the  flame  of  the 
spirit  lamp,  so  as  to  raise  the  temperature  of  the  liquid  to  a 
point  short  of  that  at  which  it  gives  off  vapor.  This  subsidiary 
test  answered  its  purpose  completely ;  the  group  of  substances 
in  Table  II.  which  had  already  given  colors,  more  or  less  cha- 
racteristic, with  the  cold  acid,  underwent  further  changes  of 
color,  more  or  less  peculiar;  while  the  group  in  Table  I.,  which 
had  undergone  no  change  with  the  cold  acid,  became  subdivided 
*  I  ought  to  state  in  this  place  that  some  of  the  alkaloids  are  very  sensi- 
tive to  heat,  so  that  a  very  slight  rise  of  temperature  is  followed  by  a  de- 
cided development  of  color.  Hence  it  is  possible  that  experiments  made 
in  a  cold  room  in  winter  may  yield  results  differing  somewhat  from  the 
same  experiments  made  in  a  warm  room  in  the  height  of  summer.  It 
must  also  be  borne  in  mind  that  sulphuric  acid,  if  not  free  from  nitric  acid, 
may  impart  to  some  of  the  alkaloids  a  tint  of  rose,  yellow,  or  buff,  suf- 
ficiently deep  to  justify  their  removal  from  Table  I,  to  Table  II.  It  may 
be  well,  therefore,  lo  state  that  the  experiments  on  which  the  tables  are 
founded  were  made  in  the  winter,  in  a  room  with  a  fire,  but  in  the  morn- 
ing, before  the  temperature  of  the  room  had  been  raised  to  a  point  ap- 
proaching summer  heat ;  and  that  the  acid  employed  was  free  from  nitric 
acid. 
