This  reaction  is  of  itself  a  strong  argument  in  favour  of  the  idea
that  hippuric  acid  is  the  amide  of  benzogly colic  acid.  This  acid
is  crystalline,  sparingly  soluble  in  cold  water,  soluble  in  alcohol
and  ether.  It  is  decomposed  by  heat,  and  even  by  boiling  with
water.  Its  salts  are  generally  soluble  and  crystallisable.  When
boiled  with  acids,  it  is  rapidly  decomposed,  yielding  benzoic  acid
and  a  new  acid,  glycolic  acid.
Glycolic  Acid,  C*  H3  05 ,  H  0  =  C*  EU  06 .  This  acid  is  formed
in  the  manner  just  described.  Thus,  Cis  H8  08  +  2  H  0  =
C14H6  0*  -j-  C4  H*  Oe.  When  purified,  it  forms  a  syrup,  like
lactic  acid,  which  is  decomposed  by  heat.  In  fact,  glycolic  acid
is  homologous  with,  and  perfectly  analogous  to,  lactic  acid,
Ce  He  Oe.  Benzoglycolic  acid  is  composed  of  dry  benzoic  and
dry  glycolic  acid.  Cis  Hs  Os  =  Ci*  H5  03  +  C*  H3  05 .  And
glycocine  (glycocoll)  is  the  amide  of  glycolic  acid.  C*  H*  Oe  +
N  H3  =  C*  N  H5  0*  +  2  H  0.  We  can  now  see  how  it  is  that
hippuric  acid,  although  it  be  the  amide  of  benzoglycolic  acid,  does
not  yield  that  acid  and  ammonia,  when  boiled  with  acids,  but
benzoic  acid  and  glycocine.  The  benzoglycolic  acid  is  at  first
formed,  along  with  ammonia ;  but  it  is  immediately  decomposed
into  benzoic  and  glycolic  acid,  and  the  latter,  with  the  ammonia,
forms  water  and  glycocine.
It  has  been  stated  that  glycolic  acid  is  the  lowest  member  of
a  homologous  series  of  acids,  of  which  the  next  is  lactic  acid.
