## The Density Bottle

The density bottle offers a quick way to measure the density of a liquid.

The density bottle consists of a bottle with a glass stopper that has a hole through the middle. When the bottle ois filled and the stopper inserted, excess liquid rises through the hole and down the sides iof the bottle. The bottle is then wiped and weighed. The mass of the empty bottle is then subtracted to give the massof a fixed volume of liquid.

The density of the liquid can then be determined using the formula density,

It is important to keep the temperature of the liquid steady, by not holding it in the hand too long. This would mean the liquid expands and some of it is lost.

The density bottle makes it easy to compare the density of liquid with the density of water, which is very close to 1 gram/cm ^{3 }. If the bottle weighs 900 grams when full of water and 1080 grams when full of some liquid, the relative density of the liquid is the same as the density of the liquid when expressed in grams/cm ^{3 }. For this liquid it is

Care must be taken though, because the density of water varies with temperature, as will the density of the liquid, and they will not in general vary in a uniform or proportional way.