Am;/prii;i^94arm'}   Gleanings  from  the  German  Journals,  197 
GLEANINGS  FROM  THE  GERMAN  JOURNALS. 
By  Frank  X.  Moerk,  Ph.G. 
Jalap  resin  has  repeatedly  been  investigated,  but  considerable 
discrepancy  existing  between  the  results,  A.  Kromer,  who  has 
made  studies  of  the  glucoside  constituent  of  several  plants  of  the 
same  natural  order,  approached  the  subject.  Convolvulin  was 
prepared  from  authentic  jalap  resin  by  first  removing  water 
soluble  constituents;  after  drying  at  a  moderate  temperature 
it  was  treated  with  several  portions  of  ether  to  remove  fats  and 
other  soluble  matter ;  the  brown  residue,  insoluble  in  ether,  was 
dissolved  in  alcohol  and  subacetate  of  lead  solution  added  until 
precipitation  ceased ;  the  supernatant  liquid  and  precipitate  was 
transferred  to  a  filter,  the  precipitate  washed  with  alcohol  until  the 
washings  ceased  to  produce  a  turbidity  when  dropped  into  water, 
and  the  excess  of  lead  precipitated  with  H2S,  the  precipitate  being 
washed  with  alcohol.  The  alcohol  was  in  large  part  recovered  from 
the  filtrate  and  washings,  the  residual  convdlvuHn  was  purified  by 
repeated  solution  in  alcohol  and  precipitation  with  ether ;  it 
formed  a  colorless  amorphous  mass,  reducible  to  a  white  powder, 
which,  during  the  operation,  became  strongly  electrified  ;  easily 
soluble  in  alcohol  and  glacial  acetic  acid,  insoluble  in  petroleum 
ether  and  ether;  concentrated  sulphuric  acid  colors  it  red  or  brown- 
ish red.  Convolvulin  is  lsevogyre,  and  has  the  formula  C61H108O27, 
which  is  deduced  from  its  analysis  and  its  decomposition  products  ; 
alkalies  decompose  it  into  one  molecule  volatile  methyl-ethyl-acetic 
acid  C5H10O2,  and  two  molecules  monobasic  convolvulinic  acid 
C28H52Ou,  which  is  amorphous,  yielding  a  white,  hygroscopic  powder 
soluble  in  water  and  alcohol,  insoluble  in  ether ;  strong  H2S04 
colors  it  red  or  brown-red  ;  by  the  action  of  acids  one  molecule 
convolvulinic  acid  yields  two  molecules  of  a  glucose  and  one  mole- 
cule convolvulinolic  acid  C16H30O3,  which  is  insoluble  in  water,  melts 
at  460  C,  is  not  colored  by  H2S04,  and  is  isomeric  with  jalapinolic 
acid  and  scammonolic  acid,  both  of  which  melt  at  63-640  C. 
Convolvulin  in  its  decomposition  by  KOH  unites  with  13-7  per  cent. 
KO  H.  This  determination  may  prove  of  considerable  value  as  a  rapid 
means  of  determining  the  purity  of  the  convolvulacese  resins,  and  is 
performed  as  follows  :  The  convolvulin  or  resin  is  dissolved  in  an 
excess  of  \n  potassium  hydrate,  allowed  to  stand  twenty-four  hours 
and  titrated  with  i/z  sulphuric  acid,  using  litmus  as  the  indicator. 
