Am.  Jour.  Pharm. 
April.  1902. 
a-  and  fi-Eucaine. 
199 
cainc  acts  like  cocaine.  The  precipitate  in  all  cases  is  lemon-yellow. 
The  a-eucaine  precipitate  is  quite  crystalline.  All  three  may  throw 
down  a  small  amount  of  a  yellow  colloidal  precipitate  which  sticks 
to  the  side  of  the  test-tube  and  dissolves  but  slowly,  although  this 
in  no  wise  interferes  with  the  test,  and  does  not  take  place  if  rea- 
gents are  added  slowly.  While  this  test  depends  upon  the  very 
much  greater  insolubility  of  the  a-eucaine  salt,  the  non-precipita- 
tion in  dilute  solutions  of  a  certain  strength  until  after  the  addition 
of  hydrochloric  acid  is  quite  characteristic  for  all.  The  correct 
strength  is  about  0-5  per  cent,  solution  of  a-eucaine  and  about  I  per 
cent,  for  /9-eucaine  and  cocaine.  In  the  case  of  cocaine  and  /3-eucaine, 
the  test  may  be  conveniently  applied  by  precipitating  a  stronger 
solution  than  I  per  cent,  with  potassium  dichromate  solution,  dilut- 
ing carefully  with  water  until  precipitate  just  dissolves.  On  addi- 
tion of  a  drop  of  concentrated  hydrochloric  acid  the  precipitate  will 
at  once  re-form.  This  cannot  be  done  with  a-eucaine,  for  precipitate 
once  formed  it  is  difficult  to  get  it  to  dissolve  at  all. 
Chromic  acid  (1  :  20)  acts  similarly  to  the  dichromate. 
REACTIONS  OF   COCAINE    DISTINGUISHING  IT   FROM   EITHER  a-  OR 
/3-EUCAINE  OR    FROM  BOTH. 
If  a  small  amount  of  cocaine  hydrochloride  be  rubbed  up  with 
dry  mercurous  chloride  (calomel),  and  then  moistened  with  alcohol, 
it  rapidly  turns  to  a  grayish  black.  a-Eucaine  hydrochloride 
becomes  slowly  a  dark  gray.  /3-Eucaine  hydrochloride  is  not 
affected. 
Platinic  chloride  throws  down  slowly  a  yellow  crystalline  pre- 
cipitate from  a  I  per  cent,  solution  of  cocaine  hydrochloride  which 
is  insoluble  in  hydrochloric  acid,  a-  and  /?-eucaine  hydrochloride 
in  1  per  cent,  solution  are  not  altered.  In  stronger  solutions  all 
three  hydrochlorides  are  immediately  precipitated  by  platinic  chlo- 
ride, but  the  cocaine  precipitate  is  not  soluble  in  hydrochloric  acid, 
while  the  precipitates  by  either  eucaine  are  at  once  dissolved. 
F.  Giezel1  has  pointed  out  that  the  permanganate  of  cocaine  is 
much  more  stable  than  that  formed  by  most  other  alkaloids.  This 
fact  gives  rise  to  one  of  its  most  distinguishing  reactions.  The  test  is 
applied  upon  a  microscopic  slide  or  in  a  small  watch-glass.  A  drop 
of  a  solution  of  the  hydrochloride  is  placed  upon  the  glass  and  a 
1  Pharm.  Ztg.y  p.  132,  1886. 
