74  Chemistry  of  Alkaloid  Estimations.  {^w^ms™* 
those  who  have  tried  the  official  process  of  estimating  strychnine  no 
doubt  experienced  that  at  times  the  method  "works,"  while  at  other 
times  it  is  plainly  seen  that  the  oxidation  of  brucine  does  not  pro- 
ceed as  it  should.  It  is  well  known  that  the  oxidizing  effect  of  nitric 
acid  depends  largely  on  conditions  of  concentration  and  tempera- 
ture under  which  it  acts  ;  thus,  Gordin  has  pointed  out  that  the 
often  incorrect  results  obtained  with  the  official  process  are  due  to 
the  fact  that  the  method  adopted  directs  the  use  of  a  nitric  acid 
having  a  lower  concentration  than  that  which  he  proposed.  Farr 
and  Wright,,  in  England,  have  studied  the  method  and  propose  to 
increase  the  oxidizing  effect  of  nitric  acid  by  allowing  the  reaction 
to  go  on  at  a  somewhat  elevated  temperature.  In  the  United  States, 
H.  M.  Webster  and  R.  C.  Pursel  have  studied  the  method  in  detail. 
They  apparently  have  solved  the  difficulties  experienced  with  this 
method  by  adding  to  the  nitric  acid  a  small  quantity  of  sodium 
nitrite  whereby  the  oxidation  of  brucine  is  insured. 
The  Assay  of-  Coca. — It  is  well  known  that  cocaine  is  the  methyl- 
benzoyl-ester  of  ecgonine  and  that  it  is  very  readily  decomposed 
with  formation  of  the  mother  substance,  ecgonine.  While,  formerly, 
in  the  manufacture  of  cocaine  great  care  was  taken  to  avoid  the 
decomposition  of  this  alkaloid,  at  the  present  time  coca  leaves  are 
treated  in  such  a  way  that  the  alkaloids  are  decomposed  so  that 
ecgonine  is  obtained.  This  body,  after  its  isolation,  is  then  treated 
so  as  to  reintroduce  the  methyl  and  the  benzoyl  group  so  as  to 
again  yield  cocaine.  When  coca  leaves  are  used  for  the  manufac- 
ture of  cocaine  their  commercial  value  depends  on  the  amount  of 
ecgonine  which  may  be  obtained  from  them,  and  accordingly 
methods  have  been  proposed  lor  the  assay  of  coca  leaves  based  on 
their  ecgonine  content.  A  method  recently  proposed  extracts  the 
total  alkaloids  from  coca  leaves  and  then  converts  them  to  ecgonine 
chloride  by  boiling  with  very  dilute  hydrochloric  acid.  After  re- 
moval of  bodies  other  than  ecgonine  chloride,  the  liquid  obtained  is 
evaporated  to  dryness  and  the  ecgonine  chloride  is  weighed. 
