Periodic acid splits glucose and fructose into formic acid and formaldehyde. Ratio of formic acid and formaldehyde from glucose and fructose is : 

The reaction is 

$\begin{array}{l}\mathrm{CHO}-\mathrm{CHOH}-\underset{\text{ glucose }}{\mathrm{CHOH}}-\mathrm{CHOH}-\mathrm{CHOH}-{\mathrm{CH}}_2{\mathrm{OH}}_{\to }^{{5\mathrm{HIO}}_4}\\ 5\mathrm{HCOOH}+\mathrm{HCHO}+5{\mathrm{HIO}}_3\end{array}$

Ratio of formic acid and formaldehyde from glucose and fructose is :  5/1 and 3/2