Fig. 1. Flux meter schematic. The meter uses the dilution of a chemical tracer to measure flow through the outlet tubing at the top of the chamber. A tracer solution of equal density but different composition than the flux fluid is injected at a constant rate by an osmotic pump into the water stream as it moves through the outlet tube. The same pump withdraws a sample of the vent fluid/tracer mixture from downstream of the tracer injection port. Each sample coil is initially filled with distilled water. Portions of the fluids moving into or out of the top of the chamber are collected in the coil, displacing the distilled water. A unique pattern of chemical tracer distribution in the two sample coils gives both polarity and aqueous flow rates allowing a serial record of the flow rates to be determined. Having two sample coils allows both positive and negative flow to be measured.