Sucrose is hdyrolysed by concentrated alcoholic solution of hydrochloric acid.
The hydrolysis is carried out at about 323 K by heating on a water bath for about two hours.
Hydrolysis gives glucose and fructose
C12H22O11 --> C6H12O6 + C6H12O6
Glucose and fructose both have the same molecular formula.
Glucose being almost insoluble in alcohol crystallises on colling while fructose being comparatively more soluble remains in the solution