A^tlmberPi9lt  \  ProPosed  Method  of  Microsublimation.  413 
chemical  experiment.  Thus,  in  chemical  literature,  sesculin  is  stated 
to  lose  its  water  of  crystallization  at  about  1300,  to  melt  at  1600, 
and  to  decompose,  yielding  aesculetin  and  dextrose,  at  about  2300. 
Tunmann  states,  however,  that  when  examined  by  the  microsubli- 
mation method,  sesculin  melts  at  49-500,  sublimes  readily  at  58-600, 
and  may  even  be  sublimed  out  of  gelsemium  at  so  low  a  temperature 
as  400,  no  decomposition  occurring.  The  author  finally  claims  that 
the  method  is  of  such  value  that  it  should  be  adopted  by  the  Phar- 
macopoeias as  a  test  for  the  identity  of  gelsemium. 
In  view  of  certain  facts,  however,  it  appeared  to  the  present 
author  that  the  subject  required  further  investigation.  In  the  first 
place,  the  suggestion  that  the  chemical  and  physical  properties  of  a 
compound  can  be  greatly  altered  by  the  conditions  under  which  it 
is  examined  cannot- be  entertained.  A  small  amount  of  a  compound 
will  melt  at  the  same  temperature  when  heated  between  two  micro- 
scope slides  as  when  heated  in  a  capillary  tube  in  the  ordinary 
manner,  and  it  will  not  become  more  volatile  by  being  examined 
under  a  microscope.  In  the  second  -place,  gelsemium  does  not  con- 
tain any  aesculin,  and  therefore  Tunmann  cannot  have  obtained 
a  sublimate  of  this  compound  from  the  drug  in  question. 
The  fluorescent  principle  in  gelsemium  has  been  shown  to  be 
scopoletin  (aesculetin  5-methyl  ether),  and  not  aesculin.3  Sonnen- 
schein,4  whose  work  is  referred  to  by  Tunmann,  stated  that  he  iso- 
lated sesculin  from  gelsemium,  but  a  consideration  of  the  method 
employed  by  him  renders  it  evident  that  the  compound  he  obtained 
could  not  have  been  the  glucoside  in  question,  and  must  have  con- 
sisted of  scopoletin.  Thus  Sonnenschein  states  that  the  drug  was 
extracted  with  a  mixture  of  equal  parts  of  alcohol  and  water, 
the  extract  concentrated,  and  deprived  of  resin.  The  liquid  was  then 
treated  with  basic  lead  acetate,  the  precipitate  collected,  suspended 
in  water,  and  decomposed  by  means  of  hydrogen  sulphide,  the 
crystalline  compound  being  obtained  by  extracting  the  resulting 
liquid  with  ether.  He  also  states  that  a  further  amount  of  "  sescu- 
lin "  was  obtained  from  the  filtrate  from  the  basic  lead  acetate  nre- 
cipitate  by  extraction  with  ether,  after  the  removal  of  the  lead  by 
means  of  hydrogen  sulphide.  Not  a  trace  of  sesculin,  however, 
can  be  removed  from  its  aqueous  solution  by  extraction  with  ether, 
3  Moore,  Journ.  Chem.  Soc,  1910,  97,  2223;  1911,  99,  1043. 
*Ber.,  1876,  9,  1 182. 
