45 2  Quinine,  CincJionidinc  and  Isomers.     { Am  morak 
is  impossible  to  say,  but  in  any  case  the  mean  values  of  205-1°  C. 
and  207-2°  C.  (corrected)  adopted  by  Lenz  for  cinchonidine  and 
quoted  in  Beilstein's  "Handbook,"  are  to  be  rejected  as  inappro- 
priate. 
When  pure  cinchonidine  is  dissolved  in  moderately  warm  sul- 
phuric acid  containing  25  per  cent.  H2SOi(  in  the  proportions  of  1 
gram  to  8  cc,  the  greater  part  crystallizes  on  cooling  the  solution  in. 
the  form  of  tetrasulphate,  and  on  examination  of  the  base  obtained 
from  that  salt  as  well  as  from  the  mother  liquor  both  will  be  found 
to  have  the  same  melting  point  as  the  original  base  ;  under  those 
conditions  there  is  no  alteration  of  the  base.  When  homocinchon- 
idine  is  treated  in  the  same  manner  there  is  a  similar  though  not 
quite  so  large  a  crystallization,  but  in  this  case  the  base  separated 
Irom  the  mother  liquor  has  a  melting  point  of  about  206°  C.  and 
that  obtained  from  the  crystals  melts  at  203°  to  204°.  By  further 
recrystallization  of  the  salt  from  dilute  sulphuric  acid  pure  cinchon- 
idine tetrasulphate  may  easily  be  obtained.  When  the  same  treat- 
ment is  applied  to  the  base  obtained  from  the  mother  liquor  a 
further  quantity  of  cinchonidine  tetrasulphate  is  obtained.  By  this 
means  it  is  not  difficult  to  convert  almost  entirely  into  cinchonidine 
the  homocinchonidine  remaining  in  the  last  mother  liquor  together 
with  some  cinchonidine. 
On  the  other  hand,  cinchonidine  may  be  easily  converted  into 
homocinchonidine.  When  the  above-mentioned  solution  is  heated 
in  a  closed  tube  to  140°  C.  for  six  or  eight  hours  no  crystallization 
takes  place  on  cooling,  and  it  is  easy  to  ascertain  from  the  melting 
point  of  the  base  in  that  case  and  from  the  behavior  of  the  neutral 
sulphate,  that  homocinchonidine  is  present.  The  acid  solution  will 
often  remain  for  several  days  in  this  condition ;  after  a  time  crystal- 
lization commences  and  proceeds  more  or  less  rapidly,  indicating  the 
reconversion  of  homocinchonidine  into  cinchonidine.  The  change 
may  be  accelerated  by  dropping  a  crystal  of  cinchonidine  tetrasul- 
phate into  the  solution,  and  thus  it  is  perfectly  easy  to  prepare 
homocinchonidine  from  cinchonidine  or  the  reverse. 
The  two  bases  are  distinguishable,  apart  from  other  differences, 
by  their  melting  points  being  nearly  six  degrees  different ;  but  the 
statements  published  as  to  this  particular  might  still  more  differ 
from  each  other  if  the  melting  points  are  not  determined  in  the 
same  manner.    Dr.  Hesse's  former  data  of  1997°  to  200-5°  aPply  to 
