Polycrystalline powders of new ternary phases and well-known binary "III-V" type antiferromagnetic gadolinium pnictides have beep prepared in seconds by rapid solid-state metathesis (exchange) reactions : GdI3 + Na(3)Pn --> GdPn + 3NaI (where Pn = pnictogen = P, As, Sb, or PxAs1-x). Following thorough mixing of the precursors, the reactions are initiated by local heating with a hot filament and the products are easily isolated by washing with methanol and water. The effectiveness of the solid-state metathesis (SSM) process is shown by comparing the precursor reaction products-to these generated by the direct combination of the elements at elevated temperatures (1000 degrees C for 100 h). Characterization techniques include powder X-ray diffraction (XRD), magnetic susceptibility, scanning electron microscopy, and energy dispersive X-ray analysis (EDX). The rapidly generated SSM products are single-phase, antiferromagnetic, XRD- and EDX-pure powders, comparable to the compounds prepared by heating the elements together for several days. Slight traces of ferromagnetic gadolinium, as revealed by field-dependent magnetization, are removed and the average particle size is increased by a 12 h anneal at 1000 degrees C. The new gadolinium phosphide-arsenide solid solutions display magnetic constants (T-N and Theta(p)) intermediate between those of their binary progenitors.