Sources of Error and Possibilities for Correction
The formula on the previous page for determining the specific gravity of solids is
sufficient to obtain an accuracy of one to two decimal places.
Depending on the accuracy you require, consider the following error and
allowance factors.
– The density of the liquid causing buoyancy depends on its temperature
– Air buoyancy during weighing in air
– The change in the immersion level of the pan hanger assembly when the sample
is immersed
– Adhesion of the liquid on the suspension wire of the pan hanger assembly
– Air bubbles on the sample
Some of these errors can be corrected by calculation. To do so, it is necessary to
proceed as follows:
– measure the temperature of the reference liquid and correct its density
accordingly
and
– define the inner diameter of the container which holds the reference liquid.
Dependence of the Liquid Density on Temperature
The density of the liquid causing buoyancy depends on the temperature.
The change in the density per °C change in temperature is in the range of
– 0.02% for distilled water
– 0.1% for alcohols and hydrocarbons.
In other words, this can show up in the third decimal place during specific
gravity/density determination.
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