by Devil » Tue 24 May 2005, 06:35:05
I'm sorry, but your 2 cents have little value. You have greatly exaggerated the toxicity and flammability and the MSDS you quote has mistaken its units. In fact, the LC50 (not LD50, which applies only to ingestion) would appear to be between 50,000 and 100,000 ppm. The clue should have hit you when you saw the LC50 figures for mouse and rat. The mouse figure should have read 386 g/m3, not ppm, which is one helluva concentration. If you had read your MSDS, you will see the time-weighted average operator exposure level is cited at 500 ppm (cited elsewhere at 1000 and 1500 ppm). This allows a worker to be permanently exposed to 500 ppm (or higher, depending on the info source) for 8 h/day, 5 days/week, 52 weeks/year without any risk of harm. As a rule, toxicologists allow a 10:1 safety margin below the least concentration observed to have caused any harm in any species, so it would require a minimum of 5000 ppm over a long period of time before there was a real risk of harm. Many industrial chemicals have much higher toxicities, such as common solvents like perchloroethylene (the stuff your dry cleaner probably uses) that some authorities limit to 25 ppm.
As for your contention that it is too flammable for use in vehicles because of its low flash point and explosivity, this is ridiculous. All fuels used in ICEs have flash points lower than "some of the parts" of the engine. Even the whisky you may drink has a flash point of 12°C, which is still lower than room temp. The important thing is the autoignition temp, cited in your MSDS at 350°C. I don't believe any part of an ICE, other than the gas in the cylinders and the electrodes of the spark plugs, ever reach anything like 350°C. In any case, your hypothesis would rule out any gas for an engine; hydrogen, methane, ethane, propane, butane, all of which "boil off like mad" at normal temps and pressures and all of which have explosive limits, often over a much wider range, and all of which have been proposed for driving cars (and have been used).
I'm not defending DME as a potential fuel source; I agree it sounds specious. I am only correcting the misinformation or disinformation you have seen fit to propagate.
Devil