You want to separate nitromethane from fuel for model planes, right? This fuel contains oil, nitromethane and methanol. I always get the nitromethane+oil by gently shaking the fuel with an approx. 10% solution of NaCl in a separating funnel (to dissolve most of the methanol), standing over night and drawing off the nitro/oil mix (lower phase). This goes straight into distillation, using a 30 cm Vigreux. After a small forerun of methanol/water the nitromethane distills. Dried over CaCl
2, filtered, ready for use.
Can't give you the exact ratios of 40% fuel/salt solution used, as I do this always by gusto and it just works fine..
Quidquid agis, prudenter agas et respice finem!