Tollens' test (Ag+/NH3): Positive for ALL reducing sugars (free -CHO or enediol-forming ketoses). Silver mirror. Glucose +, fructose +, maltose +, sucrose -.

Fehling's test (Cu2+/tartrate): Positive for ALIPHATIC reducing sugars. Red Cu2O precipitate. Same results as Tollens' for common sugars.

Benedict's test: Similar to Fehling's. Used clinically for urinary glucose detection in diabetes.

Seliwanoff's test (HCl + resorcinol): Distinguishes ketoses (cherry-red within 1-2 min) from aldoses $\frac{slow pink}{faint red after prolonged heating}$. Fructose and sucrose (hydrolyzed to fructose by HCl) give fast positive.

Molisch test (alpha-naphthol + conc. H2SO4): Universal test for ALL carbohydrates. Purple ring at junction of two layers. Positive for mono-, di-, and polysaccharides.

Iodine test: Specific for polysaccharides. Starch (amylose) → deep blue; amylopectin → violet; glycogen → reddish-brown; cellulose → no color.

Barfoed's test (Cu2+ in acetic acid): Distinguishes monosaccharides (positive quickly) from disaccharides (positive slowly or not at all). Monosaccharides reduce faster.