388 
COLOR  TEST  FOR  THE  DETECTION  OF  STRYCHNIA. 
drop  tends  on  evaporation  to  crystallize  principally  near  the 
edges  of  the  drop,  thus  forming  the  margin,  which  constitutes 
the  circular  outline  of  the  film.  It  is  therefore  the  margin  of 
the  evaporated  drop  that  will  furnish  the  most  decided  evidence 
of  the  presence  of  the  alkaloid.  By  means  of  a  blunt-pointed 
glass  rod,  the  point  of  whicli  having  been  slightly  moistened 
with  sulphuric  acid,  a  small  drop  was  placed  upon  the  margin  of 
the  film,  and  in  using  the  bichromate  test,  a  most  minute  crystal 
of  that  salt  was  placed  upon  or  pushed  into  the  drop  of  acid, 
and  ])y  means  of  a  glass  rod  the  crystal,  together  with  the  acid, 
was  drawn  around  the  margin  of  the  film.  This  mode  of  pro- 
cedure with  this  test,  although  very  delicate,  will  fail  to  detect 
the  strychnia  positively  in  this  fractional  drop.  By  superimpo- 
sing and  evaporating  successively  three  drops,  the  reaction  is 
then  rendered  quite  positive. 
In  testing  with  the  liquid  reagents  the  sulphuric  acid  must  be 
added  in  extremely  minute  quantities.-  A  mere  dot  placed  upon 
the  marojin  of  the  film  must  be  regarded  as  sufficient,  and  its 
effect  upon  the  deposit  carefully  observed.  Then  by  means  of  a 
small  pipette,  the  point  of  which  is  drawn  to  a  capillary  bore  and 
charged  with  the  reagent,  a  minute  drop  of  it  is  allowed  to  flow 
upon  the  dot  of  acid,  when  by  means  of  a  pointed  glass  rod  drawn 
around  the  margin  of  the  spot,  the  colors  created  by  the  reagent 
are  obtained  vvith  various  degrees  of  vividness  and  duration, 
according  to  the  amount  of  alkaloid  contained  in  the  deposit,  and 
the  permanganate  test  will  positively  indicate  the  l-900,000th 
of  the  alkaloid.  I  have  successfully  concentrated  a  ^  drop  by 
placing  the  porcelain  plate  obliquely  while  the  droplet  is  evapo- 
rating ;  the  drop  will  gradually  contract  on  the  glazed  surface 
to  about  one-third  of  the  space  it  would  have  otherwise  occu- 
pied, and  thus  serve  to  insure  more  positive  results.  Scrupulous 
accuracy  and  cleanliness  should  be  observed  in  conducting  these 
microchemical  manipulations.  The  reagent  ought  to  be  freshly 
prepared  from  pure  materials,  of  proper  strength,  and  used 
quantitatively  with  the  greatest  care. 
Philadelpliia,  August  28,  1870. 
