rochleder's  proximate  analysis. 
469 
bj  Persoz,  and  first  recommended  bj  C.  Oppermann  as  a  method  for  sep- 
arating several  bases  from  one  another  :  — 
The  concentrated  aqueous  solution  of  bases  is  mixed  with  tartaric  acid, 
and  then  bicarbonate  of  soda  is  added.  Oppermann  has  found  that  by  this 
method  of  treatment  quinine,  morphine,  and  bruoine  are  not  ;  on  the  con- 
trary, cinchonine,  narcotine,  and  strychnine  are,  precipitated.  Thus,  in 
many  cases  whan  two  bases  are  present,  a  separation  of  one  from  the  other 
may  be  effected  by  this  method.  By  mixing  the  fluid  filtered  from  the  pre- 
cipitate which  may  have  been  produced  by  bicarbonate  of  soda  with  a 
little  hydrochloric  acid,  and  then  a  iding  bichloride  of  platina  and  alcohol, 
it  can  be  readily  determined  whether  a  base  still  remains  in  the  solution 
or  not. 
If  we  learn  by  this  treatment  that  several  bases  are  present,  we  must 
still  ascertain  whether  the precipitateJj part  and  the  no n-precipitated part  con- 
sists of  one  or  more  bases.  The  examination  depends  on  the  principle  of 
fractional  precipitation,  and  the  estimation  of  atomic  weights  which  are  un- 
dertaken with  the  individual  jyortions  of  the  precipitated  bases.  For  the  per- 
formance of  the  examination  thirty  or  forty  grains  of  the  substance  to  be 
tested  is  necessary.  The  part  of  the  solution  precipitable  after  mixture 
with  tartaric  acid  by  bicarbonate  of  soda  is  first  separated  from  the  unpre- 
cipitable  part  and  collected  on  a  filter,  then  dissolved  in  dilute  hydrochloric 
acid,  and  half  the  quantity  of  the  solution  of  bicarbonate  of  soda  is  added 
which  was  required  to  throw  down  the  entire  quantity  of  bases.  This 
quantity  should  be  previously  ascertained  with  small  measured  quantities 
of  the  solution  of  the  bases  and  bicarbonate  of  soda.  It  is  evident  that  the 
hydrochloric  acid  solution  of  the  bases  must  be  quite  neutral — that  is,  must 
contain  no  excess  of  acid. 
The  substance  separated  by  the  first  half  of  the  precipitant,  and  the  pre- 
cipitate produced  by  the  second  half  of  the  same,  are  collected  on  filters 
and  washed,  then  dissolved  in  dilute  hydrochloric  acid,  and  mixed  with 
bichloride  of  platinum  and  alcohol.  Both  the  platina  precipitates  are 
washed  with  alcohol  mixed  with  ether,  dried,  and  heated  to  redness. 
From  the  quantity  of  platina  remaining  behind,  it  will  be  seen  whether 
one  or  more  bases  are  present.  A  closer  examination  with  reagents 
whose  behaviour  to  bases  is  known,  may  first  be  performed  with  good  re- 
sults when  the  separation  of  the  different  bases  has  been  thus  approximate- 
ly attained. 
If  we  have  by  these  means  learnt  that  the  separated  crystals  are  not  an 
organic  base,  or  a  mixture  of  such  bases,  or  rather  their  salts,  with  acetic 
acid,  they  must  be  therefore  an  indifferent  organic  body,  or  rarely  a  mix- 
ture of  several  substances  of  thatkind.  The  presence  or  absence  of  nitrogen 
— that  is,  the  presence  or  absence  of  a  body  perhaps  analogous  to  aspar- 
agine— has  been  already  decided  by  the  experiment  with  the  concentrated 
solution  of  caustic  soda  in  the  hsat. 
The  preponderating  majority  of  these  indiffeient  vegetable  substances 
