Abstract–Diffusion (wick) flames were used to study relative soot production from methanol and hydrocarbons in binary liquid solutions. Methanol-toluene and methanol-benzyl alcohol solutions, prepared with C-14 labeled methanol, were burned. Comparison of sott radioactivity with that of the binary solutions indicated that fuel-to-soot conversion is 35-40 times greater for toluene carbon-benzyl alcohol system. Increasing methanol content in the liquid fuel decreased the rate of total soot generation. No soot was collectable at concentrations above a threshold of 0.94 mole fraction methanol. This threshold was also observed in parallel soot generation studies using a visible-light spectrophone and in measurements of flame luminosity as a function of fuel composition.