Amfeeptf,'  i89o8rm'}     Quinine,  Cinchonidine  and  Isomers.  449 
1 77°  C,  was  given,  and  in  the  former  the  corrected  temperature 
176-8°  C.  The  correction  may  have  amounted  to  3  or  4  degrees, .so 
that  the  observed  temperature  would  have  been  about  1 73 0  C. 
According  to  these  observations  the  melting  point  of  the  anhydride 
would  be  decidedly  the  higher.  The  difference  may,  however,  have 
been  due  to  defects  in  the  thermometers  used,  and  Dr.  Hesse  has 
therefore  tested  the  thermometer  used  in  his  latest  observations  by 
comparing  it  with  a  normal  instrument  in  the  Physicotechnica 
Institute  at  Charlottenburg  and  in  addition  has  made  use  of  Roth's 
apparatus  to  prevent  any  possible  error.  Although  this  apparatus 
does  not  give  at  once  the  absolute  melting  point,  the  direct  observa- 
tion is  such  a  close  approximation  to  it  that  the  differences  are 
within  the  limit  of  observation,  error  and  correction  may  therefore 
be  dispensed  with.  4 
Of  the  two  preparations  previously  operated  with  only  the  quinine 
anhydride  was  available  for  further  examination  and  that  gave  in 
several  experiments  a  melting  point  of  174-4°  to  175°  C. 
The  trihydrate  prepared  for  the  other  determination  was  crystal- 
lized from  dilute  alcohol  in  long  silky  needles.  The  anhydrous 
alkaloid  obtained  from  it  by  drying  in  an  exsiccator,  and  finally  at  a 
temperature  of  120°  C,  melted  at  172°  C.  The  same  substance 
was  also  obtained  in  compact  needles  by  crystallization  from  ether, 
and  after  drying  is  melted  at  171-2°  to  172°  C.  The  same  hydrate 
prepared  by  precipitating  a  dilute  water  solution  of  quinine  sulphate 
with  caustic  soda  and  also  with  ammonia  gave  after  drying  at  115° 
C.,as  the  melting  point  of  the  dry  base  172°  and  171-4°  respectively. 
Lastly,  the  base  obtained  by  heating  the  benzene  compound 
C20H24N2O2C6H6  to  120°  C,  until  free  from  benzene,  gave  from 
171-6°  to  172°  C. 
The  melting  point  of  the  anhydrous  base  obtained  by  direct 
crystallization  is  therefore  on  the  average  174-7°  C.,and  that  of  the 
base  obtained  by  heating  the  trihydrate  or  the  benzene  compound 
is  about  171-8°  C.  In  some  recent  experiments  Lenz  found  the 
melting  point  of  the  base  obtained  from  the  benzene  compound  to 
be  171°  C,  that  of  pure  quinine  obtained  by  precipitation  being 
from  170-4°  to  174*4°  C.and  he  suggested  that  the  differences  might 
be  due  to  a  mixture  of  amorphous  and  crystalline  quinine,  but  it 
was  probably  in  most  instances  a  mixture  of  ordinary  quinine  with 
the  higher  melting  anhydride  that  he  operated  upon.    The  anhy- 
