Inscale Scales Ltd (United Kingdom) - In our series of analytical balances blog posts, we have looked at dynamic weighing, statistics and percentage weighing.
In this blog post, we look at density determination, and how an analytical balance can be used to calculate this.
Density determination can tell us a lot. For example, it can help determine the purity of a sample, and give insight into its composition. This is important for many industries where, for example, the quality of raw materials needs to be checked.
Analytical balances, which can provide precise, sub-milligram results, are ideal for a process like density determination.
What is density determination?
Density determination is the calculation of a substance’s mass per the volume it occupies. In order to carry out density determination, the substance’s mass and volume must be measured.
How is density measured?
Density is measured by the Greek letter p. Comparing mass (M) to its volume (V) gives us the density, so p = M / V. The result of this calculation is described as mass per unit volume, for example, grams per millilitre.
How is density determination carried out using an analytical balance?
There are a number of processes for measuring density. Traditionally, density would be measured using the formula above:
- The volume of the sample material is calculated
- The sample material is weighed on the analytical balance
- Mass is divided by volume as per the formula above to give the density of the sample.
However, volume can sometimes be hard to calculate accurately.
How can density be determined accurately?
The most effective way to determine density is to use a density kit. Additionally, most analytical balances have a density mode which makes determination easier.
In the case of Adam Equipment’s Luna Analytical Balance, for example, the density mode allows the user to select the type of density to be determined and then enter values to be used by the balance. Density mode works best when using the Adam Equipment density kit.
How to determine density of solids:
To determine the density of solids when using the Luna, the sample must first be immersed in liquid. This allows you to know the object’s volume, by using Archimedes’ Principle of displacement.
On the Luna, press Mode and then the Up or Down keys until 'Density Solid' appears on the display. Press Setup to enter the chosen density mode.
The type of liquid the sample is immersed in can then be selected – ‘Water’, ‘Ethanol’ or ‘Other.’
With water and ethanol, the density is calculated based on the liquid temperature – the temperature will appear on the display. Weight and temperature information will allow the balance to display the density of the sample.
How to determine density of liquids:
To determine the density of liquids, place the glass float from the density kit on the weighing pan when the balance asks for ‘air weight.’
When the balance has recorded the result, it may, as in the case of the Luna, request the weight in liquid. Add the liquid to the beaker from the density kit, and press Setup to start the liquid weighing. The weight will show on the display followed by the calculated density.
For more detailed guidance on how to determine the density of liquids using the Luna and density kit, download the Luna user manual.
Recommended analytical balances:
Many of the analytical balances from our laboratory balances range have a density mode – however we recommend the Adam Equipment Luna, as well as the Solis and Equinox along with the density kit. If you need guidance on choosing the right laboratory balance for your needs, read our blog post 10 Considerations When Buying a Laboratory Balance.
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