|MadSci Network: Chemistry|
This is an answerable question, at least to a point, but I'm afraid you'll face some practical problems if you want to manufacture this lighter fluid.
Zippo lighters use a fluid which is mostly butane, with some propane mixed in. Here is a Material Safety Data Sheet (MSDS) for this product. Notice the Physical/Chemical Characteristics section. I've run through a few calculations to determine what mixtures of propane, isobutane, and n-butane would give each of these results, and I come up with a different mixture for each property. This is the source of the first practical problem. All I can say for sure is that the amount of propane in the mixture is somewhere between 5.5% and 20% (on a molar basis). I can't determine the actual composition. Perhaps it could be determined by buying a sample of the actual product and running it through a gas chromatograph. (Of course, if you wish to make lighter fluid in order to avoid paying for a refill, this won't work.)
In addition to the problem of not knowing the exact composition of this fluid, there are several other problems. Most of them are detailed on the MSDS referenced above. The propane/butane mixture is an inhalation and ingestion hazard. It can cause dizziness, disorientation, headache, excitation, central nervous system depression, and anaesthetic effects. Ingestion of this fluid can also cause freeze burns. This page also lists some of the potential health effects of lighter fluids in general.
In addition to the problems listed above, there is the obvious problem that lighter fluid (and its constituent parts) is extremely flammable. According to the MSDS referenced above, Zippo lighter fluid is flammable at concentrations in air between 1.8% and 9.5%. Certainly, any work with these fluids should be done in an area with adequate ventilation and with proper fire fighting equipment nearby.
In short, it would be possible to manufacture this lighter fluid yourself, since it is a fairly simple mixture of readily available compounds. However, the actual composition is unknown and handling the individual components and the finished product can cause severe health and safety problems. All things considered, I think it's easier just to buy a can of refill lighter fluid from the manufacturer.
I hope that helps.
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