Urinometers are typically composed of three parts: the weight, float and stem. The weight is the lower end of the urinometer containing a mercury bulb. The float is an air-filled glass tube and the stem is marked with a scale.

The urinometer would be placed in a cylinder containing a urine sample and a reading taken from the stem. This device has been widely replaced with more efficient technologies. Its tendency to drag against the side of the cylinder can often result in inaccurate readings.
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