A series of experiments was performed in slab geometry using a mixed aqueous Pu-U nitrate with 173 and 262 g/ℓ of plutonium and uranium, respectively. Both the thickness of the slab for an ∼71-cm fixed height and the height for a 19.05-cm fixed thickness were varied for this slab, which had a 106.7-cm base length. The plutonium contained 91.1 wt% 239Pu while the depleted uranium contained 0.57 wt% 235U. These measurements using the 252Cf-source-driven neutron noise analysis method are interpreted using modified point kinetics to obtain the subcritical neutron multiplication factors. This paper summarizes the data accumulated in the measurements and their interpretation in this first application of the method to slab geometry. The results and conclusions of these experiments are (a) the capability to measure the subcriticality for a multiplying system of slab geometry by the 252Cf-source-driven noise method to a k as low as 0.70 was demonstrated; (b) the reactivities obtained by independent measurements using break-frequency noise analysis agreed with those obtained from the ratio of spectral densities within the experimental uncertainties; (c) the criteria developed in previous experiments for choosing source-detector-system configurations for which the data can be interpreted using modified point kinetics were also satisfactory for this experiment; (d) measurement times for this geometry were not significantly different from those used in cylindrical geometry and were sufficiently short to allow practical measurements; (e) the applicability of the method and understanding of the theory of the measurement method for plutonium solution systems were demonstrated; and (f) calculated neutron multiplication factors agreed with those from experiments within ∼0.02.