We report here studies on the effects of Lewis base addition on the observed luminescence of porous silicon generated non-anodically from a stain etch of <100> p-type wafers and whose surface morphology has been characterized by atomic force microscopy (AFM). Addition of dilute heptane solutions of alkyl amines such as n-butyl amine (C4H7NH2) results in dramatic quenching of the steady-state photoluminescence (PL) near 625 nm. The observed fractional changes in integrated PL intensity as a function of amine concentration have been fit to a simple equilibrium model demonstrating Langmuir-type behavior from which adduct formation constants have been calculated. These steady-state PL measurements are complemented by Fourier Transform Infrared (FT IR) spectroscopic measurements monitoring the effect of amine adsorption on the silicon hydride stretching modes [v(Si-Hx)] near 2100 cm-1. Based on these results, a physical model for the amine interactions with the porous silicon surface is presented.