julyTSr'''}  Parchment  Paper  as  a  Filtering  Medium.  313 
and  glucose.  Treated  with  chromic  acid  or  binoxide  of  lead,  synan- 
throse  yields  formic  acid.  Saccharic  and  oxalic  acids  are  produced 
by  the  action  of  dilute  nitric  acid.  With  a  mixture  of  1  p.  nitric  and 
2  or  2J  sulphuric  acid,  nitrosynanthrose  is  obtained,  which  is  explo- 
sive. 
Heated  to  140^  or  145°  C,  synanthrose  turns  brown,  gas  is  evolved, 
and  a  little  caramel  formed,  besides  dextrogyric  glucose  and  Isevulo- 
san,  which  is  left  behind  after  the  fermentation  of  the  glucose,  and 
appears  to  be  optically  inactive. 
Synanthrose  was  found  by  the  author  in  the  tubers  of  Compositce  at 
all  seasons,  though  in  variable  quantities  according  to  the  age,  so  that 
they  are  richest  in  it  when  fully  developed. 
The  new  sugar  is  in  many  respects  closely  allied  to  ordinary  cane 
sugar. — Arcliiv  d.  Pliarm.,  1871,  A'pril,  31 — 39. 
PARCHMENT  PAPER  AS  A  FILTERING  MEDIUM. 
By  Charles  R.  C.  Tichborne,  F.  C.  S.,  etc. 
The  Bunsen  filter  is  now  well  known  and  familiar  to  most  manipu- 
lators. It  merel}^  consists  of  a  funnel  and  filter  connected  with  an 
air-tight  vessel,  in  the  interior  of  which  a  partial  vacuum  can  be  pro- 
duced, either  by  a  Sprengel  or  ordinary  air  pump  ;  in  fact,  by  any 
contrivance  by  which  a  downward  pressure  of  some  considerable 
power  is  exerted  upon  the  fluid  washing  some  precipitate,  or  upon  a 
liquid  it  is  desirable  to  filter  quickly. 
To  give  us  the  opportunity  of  doing  this  properly,  it  is  necessary 
to  have  a  nicely  prepared  support  beneath  the  nozzle  of  the  filter,  to 
enable  it  to  bear  the  considerable  pressure  to  which  it  is  exposed  ; 
the  nozzle  of  the  filter  being  the  point  of  weakness.  This  is  generally 
•done  by  very  carefully  forming  a  little  cone  of  platinum  foil,  which 
must  exactly  fit  the  bend  of  the  funnel.  If  the  fit  is  not  perfect,  it 
generally  results  in  the  breaking  of  the  filter  and  the  failure  of  the 
-experiment.  This  is  at  once  obviated,  and  the  platinum  nozzle  dis- 
pensed with,  by  using  parchment  paper  as  a  filter.  Parchment  paper 
bears,  undei"  such  circumstances,  any  reasonable  pressure  ;  and  yet  it 
is  a  perfect  filtering  medium.  As  regards  the  strength.  Dr.  Hofmann 
aays  that  it  becomes  five  times  as  strong  as  the  paper  before  it  is 
parchmentized  ;  and  I  think  that,  when  speaking  of  moist  bibulous 
paper,  it  is  no  exaggeration  to  say  its  strength  is  increased  at  least 
twenty  times. 
