TESTING  FOR  STRYCHNIA,  BRUCIA,  ETC. 
551 
crystals.  I  will  let  fall  into  this  evaporating  dish  a  drop  of  the 
liquor  containing  the  chromate  of  strychnia,  and  having  shaken 
the  vessel  so  as  to  spread  out  the  drop  as  much  as  possible,  I 
will  project  on  it  from  time  to  time  a  drop  or  two  of  strong  sul- 
phuric acid,  when  the  beauty  and  intensity  of  the  effect  will  be 
strikingly  apparent.  This  may  even  be  shown  on  a  still  more 
refined  scale,  by  taking  a  crystal  or  two  on  the  point  of  a  pen- 
knife, transferring  it  to  the  edge  of  an  evaporating  dish,  and 
touching  the  spot  with  a  drop  of  sulphuric  acid. 
This  chromate  of  strychnia  may  be  obtained  in  the  amorphous 
state  from  the  neutral  chromate  of  potash  ;  in  the  nacreous  or 
irregular  crystalline  state  from  the  bichromate  ;  and  lastly,  which 
forms  a  more  striking  peculiarity,  in  the  regular  crystalline  con- 
dition— viz.,  first  in  the  form  of  fine  spiculae,  and  next  of  beau- 
tiful small  cubic  crystals,  which  completely  stud  the  sides  of  the 
glass  vessel  when  a  weak  acid  solution,  such  as  recommended  for 
the '  precipitation  of  iodine  is  used,  but  of  course,  considerably 
diluted.  This  latter  peculiarity  is  very  decided,  and  charac- 
teristic of  strychnia. 
Experiment :  30  drops  of  solution  of  acetate  of  strychnia,  8 
drachms  of  water ;  then  add  20  drops  of  the  acid  solution  of 
bichromate  of  potash  ;  let  it  crystallize  without  shaking. 
I  have  taken  some  pains  to  ascertain  in  what  respects  other 
substances  may  clash  with  this  method  by  producing  a  more  or 
less  similarly  colored  salt,  and,  as  far  as  I  have  had  opportuni- 
ties of  judging,  there  appear  to  be  only  two — viz.,  chromate  of 
brucia  and  chromate  of  lead.  But  I  conceive  that  any  Chemist, 
well  acquainted  with  their  specific  characters,  can  easily  distin- 
guish them  from  chromate  of  strychnia. 
Both  chromate  of  strychnia  and  chromate  of  brucia  are  very 
susceptible  of  discoloration — that  is,  becoming  brown  or  dark- 
colored  by  exposure  to  the  sun-light — a  property  not  possessed 
by  chromate  of  lead. 
Chromate  of  strychnia  becomes  changed  to  a  deep  purple, 
and  then  to  a  violet  and  red  when  touched  with  a  glass  rod 
dipped  in  sulphuric  acid.  Chromate  of  brucia,  on  the  contrary, 
shows  only  an  orange-red  color,  without  any  shade  of  blue  or 
violet.    Again,  chromate  of  brucia  is  so  much  more  soluble  than 
