To measure the relative density of a liquid
The easiest way to ensure getting identically equal volumes of a liquid and water is to use a density bottle (Fig. 9.2). This bottle has a ground glass stopper with a fine hole through it, so that, when it is filled and the stopper inserted, the excess liquid rises through the hole and runs down the outside. So long as the bottle is used with the same liquid level at the top of the hole, it will always contain the same volume of whatever liquid is put in provided the temperature remains constant.
The bottle is weighed empty and then when full of the given liquid. The liquid is
then returned to the stock bottle. Having well rinsed or cleaned the bottle, it is filled
with water and weighed again. Two precautions are necessary. The outside of the bottle must be wiped dry before weighing. Secondly, the bottle should not be held in a warm hand or some of the liquid may be lost through expansion. The results are set out as below. For neatness, decimal points, equals signs and so on should be arranged uniformly underneath each other.