The density of the common white vinegar found in most kitchens is 1.01 grams per milliliter.
But what does this measurement actually mean? In order to answer that question, the definition of density needs to be understood. "Density" in scientific terms indicates the mass per unit volume of a solution. Water is considered to have a density of "1.0" and every other solution is compared to this.
Since common household vinegar is 1.01, it is easy to infer that it is very slightly more dense than water. Oil is less dense than both water and vinegar, and that's why it floats on top.
The density of all solutions, including vinegar, is done by using a hydrometer. A hydrometer is a calibrated glass tube that measures the density (also called "specific gravity" of a solution).
The density of vinegar can actually change, depending on the amount of acetic acid present. Acetic acid gives vinegar its pungent taste and strong odor. Common household vinegar has a 5% acetic acid content, with a density of 1.01, as mentioned above. Other kinds of vinegar have slightly more or less acetic acid, with slightly varying densities.
Vinegar has been associated with weight loss, lowering of blood glucose levels in diabetics, and for the management of high blood pressure. None of these have been substantiated through research. And while vinegar does ease the pain of jelly fish stings, even this "miracle cure" isn't quite as effective as plain old hot water.