We have tested the feasibility of measuring the ratio of proton-neutron to proton-proton elastic scattering using the second extracted proton beam of the Argonne ZGS and a liquid-deuterium target. The forward proton was detected by a 35-m-long spectrometer consisting of magnets and scintillation and erenkov counters. The recoil nucleon was detected by a steel-scintillator sandwich counter. The efficiency of this counter was measured using tagged neutron in coincidence with the spectrometer and calculated using a Monte Carlo simulation of the nuclear cascade. A scintillation counter determined whether the recoil nucleon was charged or neutral. At a test point of p0=12.4 GeV/c, θ*=37°, and t=-2.2 (GeV/c)2, we found a pn-to-pp cross-section ratio of 1.05±0.14. The pp cross section was (dσdΩ)c.m.=5. 8±0.6 μb/sr, and the pn cross section was (dσdΩ)c.m.=6. 1±1 μb/sr. The ratio of pp scattering from deuterium to pp scattering from hydrogen, corrected for geometrical effects, was 0.75±0.09. We discuss the future of this technique for measuring pn cross sections and compare the results of the test with the predictions of the Glauber multiple-scattering formalism. We also plot available pn data as a function of βc.m.2p2.