Dynamic method for the determination of the s.v.p. of water

A method of measuring the s.v.p. of water based on the above idea was developed by Ramsay and Young in 1886. A simplified diagram of their apparatus is shown in the following diagram.

The liquid in the flask is heated until it boils and the pressure (h) within the apparatus measured with a manometer.

Saturated pressure = H - h

The large flask is included in the apparatus to minimise the effects of rapid changes of pressure during the experiment. The source of heat is then removed and the flask allowed to cool slowly. Boiling can be achieved at any temperature by reducing the pressure within the apparatus using the vacuum pump.

The water can be made to boil at 30 ^oC with a simple tap-mounted pump, the s.v.p. of water being about 3 cm of mercury at this temperature.