AmMay?i902arm*}  a~  and  $-Eucaine.  237 
become  very  small  and  numerous,  covering  the  entire  field,  while  the 
interference  colors  are  only  gray  or  black.  The  forms  of  gray  and 
black  overlying  feathers  are  at  times  very  prominent  in  a-eucaine, 
and  resemble  nothing  so  closely  as  the  small  feathers  of  Plymouth 
Rock  poultry. 
/3-Eucaine  hydrochloride  from  saturated  solution  shows  broad 
feathery  or  fern-like  forms,  sometimes  blade-like  or  tabular.  Usually 
the  tabular  forms  show  concentric  rings  of  high  color  around  the 
edges  and  the  extinction  directions  are  easily  determined.  They 
are  usually  slightly  oblique  to  the  main  axis  of  the  crystal,  but  dif- 
ferent crystals  show  two  separate  angles  of  extinction,  one  being 
the  complement  of  the  other  and  due  to  the  fact  that  the  individuals 
are  viewed  from  opposite  sides.  The  forms  already  mentioned  are 
more  apt  to  be  found  around  the  outer  edge  of  the  evaporated  drop, 
while  the  centre  is  made  up  of  isolated  individuals  which  show  bril- 
liant tabular  and  prismatic  forms,  sometimes  quite  small  and  rod- 
like. Rarely  they  are  diamond-shaped.  These  diamond-shaped 
forms  sometimes  show  extinction  directions  symmetrical  to  the 
main  axis,  but  more  often  slightly  oblique.  The  individual  crystals 
are  large  and  much  more  easily  studied  than  those  of  a-eucaine. 
If  more  dilute  solutions  of  less  than  1-5  per  cent,  are  used,  the  char- 
acteristics do  not  come  out  so  plainly,  the  crystal  forms  being 
smaller  and  showing  very  low  interference  colors,  mainly  light 
grays.  Also  these  sometimes  show  feathery  forms  and  rosette 
forms  something  like  a-eucaine. 
Cocaine  hydrochloride  in  10  per  cent,  to  1  per  cent,  solution  crys- 
tallizes in  fan-like  shapes.  A  2  per  cent,  solution  gives  a  solid  field 
of  radiating  forms,  the  individuals  of  which  resemble  very  closely 
the  forms  sometimes  seen  on  a  frosted  window.  Extinction  is 
parallel  and  perpendicular  to  the  main  axis  of  the  crystals.  Colors 
are  brilliant  and  the  whole  field  is  characteristic,  enabling  one  to 
distinguish  cocaine  immediately.  With  dilute  solutions  the  fan-like 
shapes  are  still  marked,  but  the  field  is  sometimes  broken  and  inter- 
ference colors  are  a  slow  order  of  light  grays. 
In  conclusion  it  is  perhaps  well  to  suggest  that  in  working  on 
unknown  substances  all  tests  for  eucaine  and  cocaine,  as  with  other 
alkaloids,  are  much  more  valuable  when  compared  with  those  ot 
samples  whose  identity  is  known. 
New  Hampshire  Coixege. 
