Principle

The rotation of the plane of polarisation through a sugar solution measured with a half-shade  polarimeter and the reaction rate constant for the inversion of cane sugar determined.

Benefits

• Even transparent fluids can change the properties of light passing them
• Find out how fast one type of sugar changes into another one
• Use optical methods, involving the plane of polarisation, to observe chemical processes

Tasks

1. To determine the specific rotation of cane sugar (sucrose) and lactose by measuring the rotation of various solutions of known concentration.
2. To determine the reaction rate constant when cane sugar is transformed into invert sugar.

Learning objectives

• Half-shade principle
• Optical rotatory power
• Optical activity
• Saccharimetry
• Specific rotation
• Reaction rate
• Weber-Fechner law