MANNITE  PROM  THE  OLIVE  TREE 
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MANNITE  FROM  THE  OLIVE  TREE. 
Professor  De  Luca,  of  the  Royal  University  of  Naples,  ex- 
hibited at  the  Dublin  Exhibition  a  series  of  mannites,  which 
were  very  interesting,  as  they  were  produced  from  a  new  source, 
viz.,  the  olive  tree.  This  sugar  seems  intimately  connected  with 
the  formation  of  the  oil  or  fatty  matter. 
Mannite,  the  sugar  of  manna,  mushrooms,  and  many  plants, 
is  a  substance  that  bears  a  closer  analogy  to  glycerin  than  even 
to  sugar.  Like  glycerin,  it  forms  a  nitro-compound  (nitro-man- 
nite),  which  explodes  very  violently  when  struck.  It  is  pre 
pared  by  treating  mannite  with  the  strongest  nitric  and  sulphuric 
acid.  It  forms  beautiful  fine  white  acicular  crystals,  insoluble 
in  water,  but  soluble  in  alcohol  and  ether.  If  carefully  heated, 
it  may  be  decomposed  without  explosion  ;  but  when  it  is  suddenly 
heated,  it  explodes,  but  not  with  great  violence.  It  has  been 
proposed  to  use  nitro-mannite  for  charging  percussion  caps.* 
Professor  De  Luca  has  shown  that  mannite  exists  in  different 
proportions  in  every  part  of  the  olive  tree.  He  sent  specimens 
from  the  green  leaves,  #from  the  leaves  commencing  to  turn 
yellow,  from  the  flowers,  unripe  olive,  and  the  olive  commencing 
to  ripen.  This  saccharine  principle  is  not  always  found  in  the 
same  quantity  at  all  stages  of  vegetation.  At  the  period  o 
blossoming  it  accumulates  in  the  flowers  and  diminishes  in  the 
leaves.  The  fallen  flowers,  having  once  completed  the  phe- 
nomenon of  fecundation,  no  longer  contain  any  mannite  ;  it  has 
likewise  been  found  impossible  to  obtain  the  slightest  traces  of  it 
in  the  yellow  fallen  leaves.  Mannite  exists  in  the  fruit  as  long 
as  it  continues  green — diminishing  in  proportion  as  it  ripens — 
and  disappears  entirely  when  it  becomes  perfectly  ripe,  and  con- 
tains the  greatest  quantity  of  oil.  In  a  private  communication, 
not  at  present  published,  Prof.  De  Luca  says  that  these  investi- 
gations were  commenced  in  the  year  1858.  Experiments  are 
still  going  on  to  determine  at  what  period  of  vegetation  the  fatty 
matter  was  formed  in  the  olives,  and  what  is,  or  what  are,  the 
*  Nitro- glycerin  is  used  for  blasting  rocks,  and  is  at  the  present  time 
being  successfully  used  in  making  the  heavy  cuttings  for  the  new  Dublin 
Waterworks.  Nitro-mannite,  if  it  could  be  made  available,  has  the  ad- 
vantage of  being  a  solid,  whilst  the  nitro-glycerin  is  a  fluid. 
