is the high flow rate of the dye solution which is achieved by pumping dye solution at a high pressure through the relatively narrow passageway 18 the dye solution flow rate in passageway 18 can be calculated using bernoulli 39 s equation as follows where p 1 p 2 are pressures at point 1 for example in inlet 16 and at point 2 for example in passageway 18 u03c1 density v 1 v 2 are velocities at points 1 and 2 m mass h 1 h 2 are heights above a reference plane and a 1 a 2 are cross sectional areas at points 1 and 2 one example of a satisfactory arrangement has been described in the aforementioned article by f j duarte and j a piper where h 1 u2243 h 2 and the pressure provided by a commercial pump is 8 27 u00d7 10 5 n m 2 u02dc 120 psi under these conditions for dye in ethanediol with a density of u02dc 1 kg 1 flowing from a tubular cross sectional area of 20 mm 2 into the dye cell having a cross sectional area of 10 mm 2 the flow speed at the cell was measured to be u02dc 5 ms 1 thus in order to estimate the likely flow speed in a cell with a 5 mm 2 cross sectional area we assume an identical system to that of duarte and piper and using equation 2 we calculate v 2 10 ms 1 this flow rate of the dye solution is more than sufficient to accommodate high pulse repetition frequency operation in the 5 20 khz range a satisfactory.