By neutral ${\text{FeCl}}_{\text{3}}$ only allylic and phenol can be distinguished.

By ${\text{NaHSO}}_3$ and 2,4-DNP: ketone and aldehyde both can give test.

Ketone and aldehyde can be distinguished by Tollen's reagent, Fehling's solution and Schiff's reagent.

$\mathrm{C}{\mathrm{H}}_3\mathrm{C}\mathrm{O}\mathrm{C}{\mathrm{H}}_3$ (ketone) and $\mathrm{C}{\mathrm{H}}_3\mathrm{C}{\mathrm{H}}_2\mathrm{C}\mathrm{H}\mathrm{O }$(aldehyde) can be distinguished by Tollen's reagent.$\mathrm{C}{\mathrm{H}}_3\mathrm{C}{\mathrm{H}}_2\mathrm{C}\mathrm{H}\mathrm{O}$ reacts with Tollen's reagent to give silver mirror while $\mathrm{C}{\mathrm{H}}_3\mathrm{C}\mathrm{O}\mathrm{C}{\mathrm{H}}_3$ does not react.

$\begin{array}{ccccccc}{\text{CH}}_3{\text{CH}}_2\text{CHO}& +& {\text{Ag}}_2\text{O}& \stackrel{\Delta }{\to }& {\text{CH}}_3{\text{CH}}_2\text{COOH}& +& 2\text{Ag}\\ & & & & & & \text{Silver}\\ & & & & & & \text{mirror}\end{array}$

${\text{CH}}_3{\text{COCH}}_3+{\text{Ag}}_2\text{O}\stackrel{\Delta }{\to }\text{No reaction}$