Am.  Jour.  Pharm.\ 
September,  1897.  J 
Ge hemic  Acid. 
443 
results  in  combustions  of  gelsemic  acid,  for  this  principle  is  one  of 
those  few  organic  substances  which  upon  heating  with  copper  oxide 
or  oxidizing  agents  tends  to  give  up  only  a  portion  of  its  carbon  as 
carbon  dioxide,  the  rest  separating  as  a  graphitic-like  deposit  on  the 
sides  of  the  combustion  tube,  which  the  highest  possible  tempera- 
ture cannot  remove.  Over  twenty  combustions  were  made  after 
various  methods ;  in  several  instances,  even  with  cupric  oxide  alone, 
two  of  the  combustions  would  correspond  quite  closely,  but  subse- 
quent results  did  not  justify  that  any  reliance  be  placed  upon  the 
figures.  The  various  methods  employed  were :  First,  combustion 
with  copper  oxide  in  a  bayonet  tube ;  second,  with  cupric  oxide  in 
an  open  tube  in  a  current  of  oxygen;  in  the  third  method,  lead  chro- 
mate  was  employed  ;  the  fourth  method  attempted  consisted  in 
mixing  the  gelsemic  acid  with  powdered  fused  potassium  bichromate 
in  a  platinum  boat,  and  then  burning  in  an  open  tube  into  cupric 
oxide  in  a  current  of  oxygen ;  as  fifth  attempt,  the  method  of  wet 
combustion  with  a  mixture  of  chromic  anhydride  and  sulphuric  acid 
was  attempted,  passing  the  gases  through  a  spiral  cooler,  then  over 
lead  peroxide  to  remove  sulphur  dioxide,  finally  over  calcium  chlo- 
ride, into  the  potash  absorption  apparatus  (see  American  Journal 
of  Pharmacy,  May,  1897,  p.  228).  This  method,  although  requiring 
the  greatest  care  to  prevent  the  contaminating  gases  from  passing 
over,  gave  very  good  results  in  the  analysis  of  some  of  the  deriva- 
tives of  gelsemic  acid,  while  with  the  mother-substance  discordant 
results  were  obtained.  Finally,  as  last  resort,  a  mixture  of  lead 
chromate  3  parts  and  red  lead  (mennige)  1  part  was  tried,  the  com- 
bustion being  carried  on  in  an  open  tube  in  a  current  of  oxygen. 
The  two  above-mentioned  ingredients  were  reduced  to  a  fine  pow- 
der, well  mixed,  moistened  with  water,  granulated  and  sharply 
dried  at  1500  C.  This  mixture  was  introduced  into  an  open  com- 
bustion tube  and  heated  to  dull  redness  in  a  current  of  oxygen,  then 
on  cooling  the  well-dried  sample  of  gelsemic  acid,  which  had  pre- 
viously been  mixed  with  an  ignited  mixture  of  equal  parts  of  pow- 
dered lead  chromate  and  lead  oxide,  was  introduced,  and  the  com- 
bustion carried  on  slowly  in  a  current  of  oxygen,  bringing  the  tube 
finally  to  a  bright  red  heat.  No  traces  of  separated  carbon  could  be 
found  on  the  sides  of  the  tube  after  combustion. 
The  analyses  resulted  as  follows  : 
