rogers (02/10/83)
Here at last should be an end of lead - no lead debate. When gasoline is made, it either has tetra-ethyl lead added or not added. Ethyl is a term for (quoting Webster's): 'univalent hydrocarbon radical C H ' 2 5 The term 'tetra-ethyl' means (quoting Webster's): 'containing four ethyl groups in the molecule' Also when they make premium, the amount of octane vs heptane determines if the mixture is to be called premium or not. octane is (again with Webster's): 'any of several isometric liquid paraffin hydrocarbons C H ' 8 18 heptane is (one last look at Webster's): 'Any of several isometric hydrocarbons C H of the methane 7 16 series; esp : the liquid normal isomer occuring in petroleum and used esp. as a solvent and in determining octane numbers.' Also, it seems to me that I have also heard 'ethyl' used in descibing premium leaded gas. I think this is just an example of the typical American's (of which I am one) urge to shorten words, as both regular and premium leaded gas could be considered 'ethyl-ated'. Please send all flames to '/dev/null'. Post to net.cycle any other info. -Roger
berry (02/14/83)
#R:tekmdp:-176800:zinfandel:4600002:000:1102 zinfandel!berry Feb 14 09:38:00 1983 True, octane is a saturated 8-carbon hydrocarbon, but the 'octane rating' determines whether a given blenfd of gasoline is 'premium' or not. The 'octane rating' is NOT the ratio of octane to heptane or any perversion of this number. The 'octane rating' displayed on gas pumps is the average of the 'Research method octane number' and the 'motor method octane number'. In the research method chemical wizards perform arcane rites of analysis on a sample of the gas and come up with a magic number indexed to 'iso-octane's' magic number (usually 100). (iso-octane is the isomer of octane with all 8 carbon atoms in a (more or less) straght line). The motor method consists of running the gasoline sample into an ANSI standard 1-cylinder Otto-cycle engine (Really!) and fiddling with the operating parameters (compression, spark, mixture etc.) until it starts knocking. An 'octane number' is derived from these parameters. Research numbers tend to be several points lower than motor numbers, hence the average. Berry Kercheval Zehntel Inc. (decvax!sytek!zehntel!zinfandel!berry) (415)932-6900