312  Synanthrose,  a  New  Carholiydaate.    {^'jui^i,  isn'!''- 
ON  SYNANTHROSE,  A  NEW  CARBOHYDRATE. 
By  0.  Popp. 
Some  years  ago  the  author  observed  in  the  rhizome  of  Helianthus 
tuberosus,  besides  glucose,  another  sugar.  He  has  since  found  it  in 
the  tuberous  roots  of  other  Syyiantherece  (compositoe)^  and  prepares  it 
preferably  from  dahlia  tubers,  by  precipitating  the  juice  with  subacetate 
of  lead,  removing  the  excess  of  lead  with  sulphuretted  hydrogen, 
neutralizing  the  free  acid  with  carbonate  of  magnesia,  and  evaporat- 
ing. The  residue  is  repeatedly  treated  with  small  quantities  of  alco- 
hol until  the  glucose  is  removed,  that  is,  until  the  solution  ceases  to 
have  any  effect  upon  polarized  light.  The  undissolved  portion  has  a 
brownish  yellow  color,  and  contains  inulin.  It  is  treated  with  small 
quantities  of  alcohol,  so  as  to  obtain  a  concentrated  solution  of  the 
new  suo"ar.  The  solution  is  decolorized  by  animal  charcoal,  and  poured 
into  absolute  alcohol  mixed  with  ether.  The  white  amorphous 
mass  is  dried  in  vacuo  over  sulphuric  acid.  Synanthrose  is  deliques- 
cent, readily  soluble  in  water  and  dilute  alcohol,  insoluble  in  ether. 
Insipid  in  taste,  and  without  action  upon  polarized  light,  it  is  decom- 
posed by  dilute  acids  into  dextrose  and  la;vulose,  has  then  a  sweet 
taste  and  is  now  directly  fermentable.  It  is  colored  black  by  con- 
centrated sulphuric  acid  in  the  cold,  but  not  turned  brown  by  caustic 
potassa  at  ordinary  temperature.  Nitrate  of  silver  produces  in  the 
cold  a  white  flocculent  precipitate  ;  on  heating,  reduction  takes  place. 
Mercurous  salts  are  reduced  in  the  cold ;  the  compounds  with  lime  and 
baryta  are  soluble  in  water,  but  insoluble  in  alcohol.  Subjected  to 
dry  distillation,  carbonic  acid,  carbonic  oxide  and  marshgas  are 
obtained,  besides  an  aqueous  distillate  containing  acetic  acid  and 
aceton. 
After  repeated  precipitation  by  alcohol  and  ether,  and  drying  in 
vacuo,  as  above,  its  elementary  analysis  gave  results  corresponding 
with  the  formula  G^JI^^^^^.^  The  baryta  compound  has  the  formula 
CiaHgoBaOii.  Alcoholic  solutions  of  subacetate  of  lead  and  synan- 
throse produce  an  amorphous  precipitate  =  C^2'^l2oPb20ii,  which  is 
soluble  in  dilute  acetic  acid  and  in  the  lead  solution. 
Synanthrose  prevents  the  precipitation  of  cupric,  ferric  and  chromic 
oxides  by  alkalies.  Freshly  precipitated  ferric  oxide  is  dissolved  by 
a  solution  of  synanthrose ;  on  evaporation,  ferrous  oxide  is  formed 
^  0=12,  0=16. 
