"Jay Honeck" wrote in message
oups.com...
Plop-plop, fizz-fizz... :-)

In a previous thread I outlined the new (vastly more convenient)
"alka-seltzer method" of testing your mogas for both ethanol and water
-- but (for those who missed it) here it is again:

1. Tap a few ounces of suspect gas into a cup
2. Drop 1/4 of an alka-seltzer into the gas
3. If no fizz, no alcohol or water is present, and the gas is "good"

The question was/is: Is it chemically valid to expect alka-seltzer to
fizz in the presence of alcohol?

Mary (with her minor in chemistry) and I (with my English degree that
allows me to, er, write about this) devised the following empirical
test:

Part I:

1. Purchase a bottle of 95% pure isopropyl (rubbing) alcohol. While
it's not ethanol, Mary determined that the chemical make-up is similar
enough for this test.

2. Pour a few ounces into a cup.

3. Add 1/4 tablet alka-seltzer to the alchohol.

4. Observe results.

** Sure enough, the tablet instantly starting fizzing.**

Part II:

1. Go to gas station we always buy our gas from.

2. Pump a few ounces into a cup.

3. Add 1/4 tablet alka-seltzer to the cup.

4. Observe results.

** Sure enough, the tablet just sat there -- no fizz.**

Part III:

1. Add some alchohol to aforementioned cup of gas, approximating a 10%
mixture.

2. Observe results.

** Sure enough, the tablet instantly started fizzing, verifying that it
WOULD fizz if there were alcohol in the gas. **

There are a few questions yet to answer

1. Since isopropyl alchohol is 95% pure, that means that it is 5%
water. Is the tablet fizzing only because of the 5% water?

2. However, even if this were the case, would it not also be true that
the presence of ethanol in the car gas would ALSO introduce water, and
thus fizz the alka-seltzer regardless? In other words, is it
irrelevant that the alka-seltzer might only be fizzing because of the
water, if water always accompanies alcohol in gas?

Either way, the fizzing would indicate the presence of water OR
alcohol, or just alcohol that is "saturated" with water -- both of
which would indicate a "No Buy".

Right?
--
Jay
others have already commented on the alka seltzer chemisty, but a simpler
and quantitative way of measuring how much alcohol is in the fuel is to
simply mix it with water. Try 9 parts of fuel to 1 part of water in a
graduated cylinder. the alcohol will migrate to the water phase so you will
see an increase in the height of the water layer at the bottom and a
decrease in the height of the fuel layer if there is significant amount of
alcohol..
terry