Am'jIa0nU?lI9h3arm•}      Recent  Work  in  the  Sugar  Group.  35 
quantities  of  d-  and  1-mannonic  acids,  the  inactive  manno-  series  is 
obtained.  Fructose  may  be  reconverted  into  glucose  by  first  reduc- 
ing it,  when  mannitol  is  formed ;  this  is  next  oxidized  to  mannose 
and  then  to  mannonic  acid,  and  from  the  latter  glucose  is  prepared 
as  described  above. 
In  addition  to  its  reactions  with  sugars,  phenylhydrazine  has 
proved  very  useful  in  identifying  the  acids  -  obtained  from  them  by 
oxidation.  It  combines  with  acids  forming  compounds  called 
phenylhydrazides,  analogous  to  acid  amides,  as  shown  by  the 
general  formula  RCO  NH-NHC6H5.  The  hydrazides  of  the  acids 
resulting  from  the  oxidation  of  sugar  are  well  characterized 
substances. 
By  further  oxidation  of  the  monobasic  acids  obtained  from  the 
hexoses  (hexonic  acids),  dibasic  acids  are  formed.  The  three 
glucoses  give  rise,  respectively,  to  d-,  1-  and  i-  saccharic  acid,  galac- 
tose to  mucic  acid,  etc.  If  d-saccharic  acid  is  reduced  with  sodium 
amalgam,  an  aldehyde  acid  COOH(CHOH)4CHO,  known  as  gly- 
curonic  acid,  first  results,  and  by  further  reduction  of  this  a 
monobasic  alcohol-acid  COOH(CHOH)4CH2OH  is  obtained.  This 
acid,  though  represented  by  the  same  plane  formula  as  gluconic 
acid,  is  not  identical  with  the  latter.  It  is  termed  d-gulonic  acid, 
and  the  sugar  obtained  by  reducing  it  is  termed  d-gulose.  L-gu- 
lonic  acid  is  obtained  by  hydrolyzing  the  cyanhydrin  of  xylose 
C5H10O5  (the  product  of  hydrolysis  of  wood-gum),  and  1-gulose  by 
reduction  of  the  acid.  The  alcohol  corresponding  to  d-glucose  is 
d-sorbitol,  and  that  corresponding  to  1-gulose  is  its  optical  isomer 
1-sorbitol. 
A  very  interesting  portion  of  this  work  is  the  formation  of  new 
sugars  containing  seven,  eight  or  nine  atoms  Of  carbon  in  the 
molecule.  .  If  an  aldose  is  acted  on  with  hydrocyanic  acid,  a  cyan- 
hydrin is  formed,  which  on  hydrolysis  gives  a  carboxylic  acid  con- 
taining one  more  carbon  atom  than  the  original  sugar.  The 
alcohol-acids  so  obtained  very  readily  form  lactones  or  internal 
anhydrides,  and  by  reduction  of  the  lactones  with  sodium  amalgam 
the  corresponding  sugars  can  be  obtained  Thus,  from  mannose, 
the  cyanhydrin  having  the  formula  CH2OH(CHOH)4CH(OH)CN) 
is  obtained,  and  this  on  hydrolysis  gives  mannosecarboxylic  or 
manno-heptonic  acid  CH2OH(CHOH)5COOH,  from  which  manno- 
heptose  and  manno-heptitol  are  formed  by  reduction  ;  the  latter  is 
