Cardmelization  in  Rivas's  Test. 
{Am.  Jour.  Pharm. 
April,  1910. 
In  the  presence  of  the  alkali,  the  glyceric  acid  thus  formed  is 
transformed  into  lactic  acid  and  oxalic  acid : 
CH..OH 
1 
CHOH 
I 
COOH 
COOH 
I 
CHOH 
I 
CH2OH 
> 
CH3 
I 
CHOH 
| 
COOH 
COOH 
I 
COOH 
Esterification  then  takes  place  between  the  lactic  acid  and  the 
pyrocatechinol,  formed  earlier  in  the  process,  with  the  formation 
of  two  isomeric  esters  of  hydrocaffeic  acid,  one  of  which  has  acid 
properties  and  the  other  alcoholic  properties : 
CH3 
I 
CHOH 
I 
COOH 
CH 
HOC  |      j  CH 
HOC  \/  CH 
CH 
CH3 
HC  OC 
HOOCHOC 
CH 
CH 
CH 
CH 
CH3 
CHOH 
I 
COOH 
HOC 
HOC 
CH 
j  CH  =  H20 
CH 
CH 
CH3 
I 
CHOH  CH 
I  /\ 
cooc  i 
HOC  \  ) 
CH 
CH 
CH 
These  citations  serve  to  show  the  complexity  of  the  changes 
when  glucose  is  heated  with  alkali,  and  to  suggest  the  desirability 
uf  further  work.  But  they  lend  no  color  to  the  assumption  of  the 
formation  of  caramel,  and  they  do  not  conflict  with  the  explanation 
already  suggested. 
It  seems  likely  that  the  yellow  color  developing  at  first  when 
glucose  is  heated  with  an  alkali,  as  in  Rivas's  Test,  is  due  to  some 
sodium  glucose  compound  of  the  nature  of  an  alcoholate.  On 
further  heating,  the  major  part  of  the  glucose  is  transformed  into 
lactic  acid  and  other  of  the  organic  acids  mentioned  by  Gaud,  and 
part  of  it  is  resinified  as  a  result  of  its  aldehyde  group.  Aldehydes 
as  a  class  exhibit  this  latter  behavior  with  alkalies.    Thus,  if  acet- 
