126  The  Assay  of  Coca.  { ^Varch.wo^- 
The  relationship  existing  between  these  bodies  can  easily  be  seen 
from  an  inspection  of  the  following  structural  formulae: 
ECGONINE.  COCAINE. 
HC!I     \Q*h  HCil     i  CH2 
HC»alC/H  HCl|f 
C 
N  •  CH,  X  _  N  •  CH, 1 
H 
CH-0(COC6H5)-CH2'COOCH 
CINNAMYL  COCAINE.  ISATROPYE  COCAINE. 
CH9 
HCf 
CH2 
H 
HC^  V  hc"  a  1    /H  CH* 
C 
N-CH3\      /O-CCKCHiCH-C^        N  CH3  \        ,0  '  CO  '  C  *  C6H5 
CH 
CH; 
It  is  the  readiness  with  which  the  methyl  group,  attached  to  the 
carboxyl,  is  split  off,  forming,  in  the  case  of  cocaine,  a  body,  viz., 
benzoyl-ecgonine,  which,  although  possessing  alkaloidal  property 
as  regards  its  behavior  to  precipitants  of  such,  is  nevertheless  vir- 
tually insoluble  in  most  of  the  solvents  (ether,  chloroform,  etc.) 
employed  for  abstracting  the  alkaloids  from  their  solutions  after 
rendering  alkaline,  that  the  discrepancy  above  referred  to  is  most 
likely  due. 
This  saponification  occurs  quite  readily,  both  in  alkaline  and  acid 
solutions,  and  slightly  so  in  neutral  solutions  with  the  progress  of 
time,  but  to  a  marked  extent  if  there  be  much  elevation  of  tempera- 
ture. 
Hence  it  is  apparent  that  a  large  excess  of  alkali  employed  both  in 
the  liberation  of  the  alkaloids  from  their  existing  combinations  in 
the  leaf,  and  their  subsequent  precipitation  from  the  solution  of 
their  salts,  prior  to  extracting  and  weighing,  is  to  be  especially 
avoided. 
This  excess  is  not  only  to  be  avoided,  but  the  strength  also  of 
the  alkali  itself  should  be  as  low  as  is  consistent  with  a  complete 
liberation  of  the  bases. 
So  also  must  the  strength  of  acid  employed  for  removing  them 
from  the  menstruum  used  be  carefully  regulated. 
