A graduated glass cylinder, usually 1000 milliliters (ml), is used for this test. Put 250ml of the gasoline to be tested into the graduated flask.
Add 50ml of water to the flask containing the 250ml of sample gasoline.
Seal the top w/a stopper and thoroughly agitate the sample. Let this rest for a couple minutes.
If there's no alcohol in the sample, there will still be only 50ml of water that has separated into a layer at the bottom of the container.
If there IS alcohol present in the sample, the amount of water/alcohol at the bottom of the container will have increased by the amount of alcohol that's present in the 250ml sample.
Subtracting the original 50ml of water that was added at the start of the test from what is now there is the percentage of alky that has been added to the gasoline.
Warning Note: Be aware that if there is also water in the test sample, the water will be included in the amount seen at the bottom of the graduated vessel. One would assume that any amount seen in the test sample that exceeds the listed amount of alcohol (either 85% for E85 or 10% for E10) would be water. But unfortunately, the regulations for alcohol content of our gasoline is such that there can be anywhere from 70% to 85% for E85, and cannot be above 10% alcohol for E10, but is CAN be lower. If it IS lower, there can be water in the fuel that will appear to be just alcohol, unless the quantity in the layer is above 10%. Even then, the amount of water could be easily assumed to be less than what is actually contained in the fuel.
Larger amounts of water will cause two layers to separate out at the bottom of the vessel when testing alcohol-containing fuel if the amount of water is sufficient to saturate the alcohol. The bottommost layer will be water, then water/alcohol, then gasoline.
