Methanol, acetic acid
As Randy mentioned, NOPOX is Ethanol and Acetic Acid with trace amounts of Methanol and Isopropanol. The Methanol and Isopropanol are not needed and are only impurities. In the original thread on RC, I worked out my own recipe that used stove alcohol, as vodka (ethanol) locally costs as much as NOPOX to buy. The stove alcohol I used had a bit more methanol than in the NOPOX recipe (90% ethanol, 10% methanol), but I used it for a year or so and had no issues with it.
Dennis