[net.cycle] leaded vs unleaded gasoline

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