Am.^our.^Ph^arm ,  I      Extraction  of  Alkaloids  fr 07)1  Cincliona. 
625 
in  proportions  equivalent  to  those  quoted  above,  a  slight  difference  will 
be  observed  in  the  results  obtained  when  nitric  acid  is  employed,  the 
amount  of  alkaloid  being  less  by  a  few  centigrammes  than  that 
obtained  by  hydrochloric  acid.  The  latter  acid  dissolves  a  colored 
substance  contained  in  cinchona  bark,  which  is  not  alkaloid,  but 
which  behaves  towards  hydrochloric  acid  as  if  it  were  so.  This 
substance  is  not  soluble  in  nitric  acid.  If,  therefore,  the  total  alka- 
loids extracted  by  hydrochloric  acid  are  afterwards  treated  with  dilute 
nitric  acid,  the  whole  of  the  alkaloids  will  be  redissolved,  leaving  a 
very  small  quantity  of  brownish  matter  unacted  upon.  I  believe  the 
behaviour  of  this  brown  residue  to  be  one  of  the  causes  of  discrepancy 
in  analyses  of  bark  performed  by  different  methods. 
To  show  that  cinchona  bark  cannot  be  completely  exhausted  of  its 
alkaloids  by  dihite  sulphuric  acid,  20  grammes  of  powdered  bark 
(ascertained  to  contain  6*72  per  cent,  of  total  alkaloids  by  the 
hydrochloric-acid  process  above  described)  were  treated  with  an  equiv- 
alent quantity  of  sulphuric  acid  employed  in  the  same  manner.  The 
first  percolate  (100  cc.)  was  of  a  much  paler  color  than  that  obtained 
by  hydrochloric  acid ;  it  was  rendered  only  slightly  turl)id  by  caustic 
soda,  or  by  HgI,KaI,  and  was  only  slightly  reddened  by  the  former. 
The  percolation  was  continued  until  677  cc.  had  been  recovered.  This 
large  volume  (more  than  thirty-three  times  the  weight  of  the  bark) 
yielded  only  0*807  gramme,  or  4*035  j)er  cent,  of  alkaloid.  Percola- 
tion was  therefore  resumed  until  a  further  800  cc.  were  recovered, 
which  yielded  0*063  gramme  alkaloids.  The  total  results  from  1,477 
cc.  percolate  (more  than  70  volumes)  was  therefore  only  0*807 +  0*063 
=  0*87  gramme,  or  4*35  per  cent.,  from  a  bark  known  to  contain  6*72 
per  cent.  From  this  it  must  be  concluded  that  sulphuric  acid  is  prac- 
tically incapable  of  extracting  the  whole  of  the  alkaloids  of  cinchona 
bark. 
Before  j^roceeding  to  speak  of  the  practical  application  of  the  above 
process,  I  may  explain  why  I  have  always  insisted  upon  the  use  of 
cold  dilute  acids  in  operating  upon  cinchona  bark. 
If  bark  powder,  which  has  been  completely  exhausted  of  its  alka- 
loids by  cold  hydrochloric^  acid,  be  heated  to  ebullition  with  more 
dilute  HCl,  and  the  liquid  after  being  strained  be  accurately  saturated 
by  caustic  soda,  a  voluminous  red  precipitate  is  formed  resembling  the 
so-called  pectic  substances  described  by  Fremy,  but  containing  not  a 
trace  of  alkaloid.    The  intrusion  of  this  matter  makes  the  extraction 
40 
