How many drops of oil does it take to pollute a gallon of water?
A standard measure of oil pollution in water is 10 ppm (10 parts
oil per 1,000,000 parts water). As a gallon of water weights 10 lbs
(Imperial gal) or 8 lb (US) gal) the weight od a gallon is about
4.54 kg, or 4540 gm and there are usually thought to be 40 drops in
a ml a drop of oil weighs about 0.02 gm.
So 1 drop in gallon would be 0.02 gm in 4540 gm or 1 gm in 225000
gm (4 ppm). Indicating that 2.5 drops would pollute 1 gallon of
water to the 10 ppm level