102 
ON  COLCHICIA. 
nitric  acid  produces  it  likewise,  but  it  changes  more  rapidly  to 
yellow.  Sulphuric  acid  with  a  trace  of  chromate  or  bichromate 
of  potassa,  or  of  sesquichloride  of  iron,  or  of  binoxide  of  lead, 
shows  the  same  reaction  at  the  point  of  contact  with  colchicia  ; 
the  liquid  itself  has  a  green  color  with  the  first  two  reagents, 
owing  to  their  intense  yellow  color. 
One  grain  of  colchicia  was  dissolved  in  one  fluidounce  of  dis- 
tilled water,  slightly  acidulated  with  muriatic  acid ;  by  repeated 
trials  it  required  114  drops  from  this  vial  to  make  one  fluidrachm; 
this  measure  had  been  carefully  gauged  with  a  pipette  graduated 
into  T-Jo  COM.  In  making  the  following  experiments,  a  suffi- 
cient amount  of  the  reagent  was  added  to  enough  distilled  water 
to  make  one  fluidounce,  and  the  solution  of  colchicia  was  care- 
fully dropped  in  until,  after  stirring,  a  permanent  turbidity  was 
observable.  Under  these  circumstances,  it  was  required  of 
Mayer's  iodohydrargyrate  of  potassium  15  drops — turbidity  quite  distinct. 
Sonnenschein's  phosphomolybdic  acid  20  "  turbidity  distinct. 
Tannic  acid  100    "      turbidity  scarcely  ob- 
servable. 
It  follows  from  this  that  the  following  amounts  of  colchicia 
may  be  detected  by 
Mayer's  test  *01645  grains  or  one  part  in  27700  water.* 
Sonnenschein's  test         -02193  "         "  20778  " 
Tannic  acid  '10965  "  "  4156  " 
Solutions  of  colchicia  in  water  acidulated  with  sulphuric  and 
with  muriatic  acid  were  evaporated  and  three  times  taken  up  by 
water  and  again  evaporated ;  the  aqueous  solutions  were  finally 
filtered  from  the  separated  resin,  and  the  filtrate  slowly  evapo- 
rated with  an  excess  of  carbonate  of  lead,  the  residue  then 
treated  with  strong  alcohol  and  slowly  evaporated.  Colchicein 
was  obtained  in  yellowish  crystals,  which  were  free  from  acid  and 
lead.  Dissolved  in  water  it  still  yields  precipitates  with  tannin, 
phosphomolybdic  acid  and  iodohydrargyrate  of  potassium ;  but 
neither  in  solution  nor  in  substance  does  it  produce  any  reaction 
on  red  or  blue  litmus  paper.  Rendered  faintly  alkaline  by  am- 
monia, the  solution  occasions  precipitates  with  the  soluble  salts 
of  barium,  calcium  and  lead,  which  are  soluble  in  dilute  nitric 
acid.    Towards  acids  it  behaves  similar  to  colchicia. 
*  One  fluidounce  water  =  455  669  grains. 
