D(+) Glucose has melting point 146°C and specific rotation [α]²⁵ D is + 112°C. Another D (+) Glucose has melting point 150°C and specific rotation[α]²⁵ D is + 18.7°C. The two form have significantly different optical rotation but when an aqueous solution of either form is allowed to stand, it rotation changes. The specific rotation of one form decreases and rotation of other increases until both solution show the same value + 52.7°. The change in rotation towards an equilibrium value is called mutarotation.