When conducting traixial tests on soil samples, it is observed that due to internal pressure, the cell expands, soil specimen consolidates resulting in the change of volume. Volume change gauge is therefore deviced to accurately measure volume changes. This is measured by observing the quantity of water entering or leaving the cell as the cell pressure and axial load are changed it is achieved by the displacement of free surface between the water supplied to the cell and another fluid (paraffin or kerosene). A dye is added to the paraffin for clear demarcation of the interface. 
The unit consists of a glass graduated tube of the appropriate capacity graduated to parts of a ml. enclosed in a perspex tube sealed by two end caps. The unit is fitted with manifolds and valves which enable it to be used with the triaxial cell and the constant pressure (Mercury controls) system. The cell pressure can either be directly applied to the cell from the constant pressure system or through the volume change gauge. The graduated glass tube is not subjected to any difference in pressure and its inside is coated with a layer of silicon water repellent to reduce the error in meniscus. There is an arrangement for filling the unit with water and paraffin and a drainage valve is provided in the lower end cap. The whole assembly is mounted on a panel suitable for wall mounting. The unit is supplied complete with a pressure hose with end couplings and a packet of dye.
Salient Features

• Single Burette -10ml capacity graduated in 0.05ml division
• - 25ml capacity graduated in0.1ml division
• Twin Burette - 50ml. capacity graduated in 0.2 ml. divisions. The unit consists of two glass graduated burettes of 50 ml. x 0.2 ml. capacity enclosed in two perspex tubes sealed by two end caps. The manifold with valves enable the flow of fluid in the burettes to be reserved when the paraffin interfaces reach their limits in the burettes, the maximum capacity of measurement being only limited by the capacity of the mercury pots. The two burettes, enable the reduction in error in meniscus reading due to reversal of flow, the average of the two burettes being always taken as the volume change reading.