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E. A. Rodriguez co-investigated aqueous waste-glass dissolution in PNNL's FY2000 study, which varied solution conditions while measuring constituent release.^[ref]

For the single-pass flow-through leach test, an inlet blank distinguishes material released by the glass from material already present in the feed. Without that subtraction, a small measured outlet concentration need not represent a small net corrosion flux.

Incongruent dissolution occurs when a solid releases its constituents into solution in proportions different from its bulk stoichiometry. Preferential release of one constituent, or dissolution accompanied by formation of a secondary solid, can both produce this behaviour.

For a nominal solid $A_a{B}_b$, congruent release would give dissolved amounts in the ratio $a:b$ if no other sinks intervene. An outlet ratio different from $a:b$ therefore motivates checking for selective leaching, precipitation, adsorption and surface alteration. It does not alone prove which step controls the rate. Distinguishing these processes matters when using a single-pass flow-through leach test to infer long-term durability from measured solution concentrations.

J. L. Steele contributed to the PNNL study of waste-glass dissolution using controlled flow-through experiments. The joint report relates measured element release to glass durability.^[ref]

The single-pass flow-through leach test measures exported material, not simply a change in the specimen's apparent size. A comparison of released constituents also tests whether the dissolution follows the solid's bulk stoichiometry.

Use a single-pass flow-through leach test. A controlled leachant passes once over a known glass surface area, and successive effluent samples are analysed after the initial transient. temperature and pH are controlled, and fresh solution removes dissolved products so that they do not accumulate towards saturation with respect to the dissolving glass. This approaches the forward glass dissolution rate at those specified conditions.

At steady state, with $Q$ expressed as volume per time,Increase $Q/S$ across a series of tests until the normalised rate becomes independent of further dilution, within analytical uncertainty. A genuine plateau supports approach to the dilute-solution limit; it should not be assumed from one arbitrarily chosen flow rate. Check blanks, inlet concentrations, temperature, pH, actual flow, fines and exposed surface area. At high flow the concentration increment becomes small, so an uncorrected background can manufacture an apparent rate increase.

The resulting maximum is the forward rate for the specified temperature, pH and glass, not an absolute maximum over every possible environment. It also differs from the lower residual rate that can develop in a static, product-rich leachate. Primary measurements demonstrate the method and the importance of background subtraction and flow variation.^[ref]

A single-pass flow-through leach test measures the dissolution of a solid while fresh solution continuously enters a reaction cell and the outlet solution is collected for analysis. Unlike a closed vessel, the cell continually exports dissolved constituents. A reported implementation uses a pump, a solution reservoir, a reaction cell and controlled temperature.^[ref]

At steady state, an elemental mass balance gives the normalized release ratewhere $Q$ is the volumetric volumetric flow rate, $c_e$ is the mass concentration of element $e$, $f_e$ is its initial mass fraction in the solid, and $S$ is the exposed surface area. For example, using litres per day, grams per litre and square metres gives grams of equivalent solid per square metre per day. This expression follows by dividing the exported elemental mass per day by $f_{e}S$.

Changing $Q/S$ changes the accumulation of dissolved material and therefore the chemical affinity for dissolution. A rate independent of further increases in $Q/S$ can help identify a dilute-solution regime. Different elemental release rates can also reveal incongruent dissolution or retention in secondary phases, so interpreting a release rate as whole-solid loss requires an explicit material model.