PYCNOMETERS

Laboratory Pycnometers for Density Determination

Pycnometers are laboratory instruments used to determine the density of substances by measuring the mass contained in a known volume. They are used to analyse liquids and, with specific designs, to determine the density of certain solid materials.

They enable density measurements using a gravimetric procedure, distinguishing them from instruments such as hydrometers, which measure by flotation.

At Pobel, you can find various laboratory pycnometers, including Gay-Lussac pycnometers, pycnometers for solids and Hubbard pycnometers.

What Is a Pycnometer?

A pycnometer is a laboratory vessel with a defined volume that allows the density of a sample to be determined from its mass and the instrument’s known volume.

For liquid pycnometers, the vessel is filled to the level specified by its design. Once the mass of the empty pycnometer and the mass of the pycnometer containing the sample are known, the mass of the liquid contained in that volume can be determined.

ISO 3507 specifies requirements for a range of general-purpose pycnometers intended for determining the density of liquids.

What Is a Pycnometer Used For?

A pycnometer is primarily used for density determination in the laboratory.

Depending on the instrument’s design, it can be used with different types of samples. Conventional models are intended for liquid analysis, while other pycnometers are specifically designed for solid materials.

Before selecting a pycnometer, it is therefore necessary to check both the sample type and the analytical procedure to be followed.

How Does a Pycnometer Work?

The measurement method involves accurately establishing the volume occupied by the sample inside the pycnometer and determining its mass by weighing.

In general, the procedure requires comparing different weighings of the instrument, for example, weighing the empty pycnometer and then weighing it with the sample inside.

The density can then be determined from the sample’s mass and the corresponding volume. The exact procedure depends on the type of pycnometer, the substance being analysed and the test method used.

The Difference Between a Pycnometer and a Hydrometer

Both pycnometers and hydrometers can be used to determine density, but they use different measurement principles.

• Pycnometer: determines density from the mass corresponding to a known volume.
• Hydrometer: in its traditional glass form, determines density or relative density by floating in the liquid.

If you need to measure by flotation, explore our range of laboratory hydrometers.

The choice between these instruments depends on the analytical method, sample type and required measurement conditions.

Types of Laboratory Pycnometers

Different pycnometer designs are available depending on the sample and measurement procedure. Pobel’s range includes several specific configurations.

Gay-Lussac Pycnometers

Pobel’s Gay-Lussac pycnometers feature a ground-glass capillary stopper and can be supplied calibrated or uncalibrated. Calibrated models include an individual certificate.

Pobel offers capacities of 5, 10, 25, 50 and 100 ml in this range.

Gay-Lussac Pycnometers with a Thermometer

Pobel also offers Gay-Lussac pycnometers incorporating a thermometer with a range of 10 to 35 °C and 0.2 °C scale divisions.

These models are available in capacities of 10, 25, 50 and 100 ml and can be supplied calibrated or uncalibrated. Calibrated versions include an individual certificate.

Pycnometers for Solids

Pobel’s pycnometers for solids are intended for determining the density of bituminous materials and minerals.

They are made from borosilicate glass 3.3, calibrated at 20 °C and available in capacities of 500, 1000 and 2000 ml.

Hubbard Pycnometers

The Hubbard-Carmick pycnometers sold by Pobel are intended for determining density or specific gravity and can be used with solids or liquids.

The available model has a capacity of 25 ml, is made from borosilicate glass and is specified in accordance with ASTM D70.

Calibrated and Uncalibrated Pycnometers

Pobel’s range includes models that can be supplied calibrated or uncalibrated.

Calibrated Gay-Lussac pycnometers are supplied with an individual certificate. This allows laboratories to select the appropriate version according to their documentation and metrological requirements.

Before choosing a model, check whether the working procedure requires a calibrated instrument and which documentation must accompany it.

Why Is Temperature Important When Using a Pycnometer?

The density of a substance can change with temperature, so this parameter must be taken into account during density determination.

For this reason, some pycnometers incorporate a thermometer, while others are calibrated at a specific temperature. Pobel’s pycnometers for solids, for example, are calibrated at 20 °C.

Measurements must always follow the conditions specified by the analytical procedure used.

How to Use a Laboratory Pycnometer

The exact procedure depends on the type of pycnometer and the sample, but determining density with this instrument requires careful control of the volume and the weighings performed.

Factors to consider include:

• Keeping the pycnometer clean and dry when required by the procedure.
• Performing weighings according to the test method.
• Filling the vessel correctly according to the pycnometer’s design.
• Avoiding sample loss or contamination during handling.
• Controlling temperature when it forms part of the test conditions.
• Using the appropriate type of pycnometer for the sample being analysed.

The specific method must always follow the standardised or internal procedure used by the laboratory.

How to Choose a Pycnometer

Before buying a laboratory pycnometer, determine the type of sample to be analysed and the requirements of the procedure.

The main factors to check are:

• Sample type: liquid or solid.
• Pycnometer design: Gay-Lussac, a model for solids, Hubbard or another configuration.
• Capacity: Pobel offers different capacities depending on the instrument range.
• Calibration: some models can be purchased calibrated or uncalibrated.
• Temperature: certain models incorporate a thermometer or are calibrated at a specific temperature.
• Analytical method: select an instrument compatible with the procedure to be followed.

Reviewing these parameters helps you choose a pycnometer suited to the laboratory’s actual working conditions.

Frequently Asked Questions About Pycnometers

What Is a Pycnometer Used For?

It is used to determine the density of a sample from the mass corresponding to a known volume.

Can a Pycnometer Be Used for Liquids and Solids?

It depends on the design. Some pycnometers are intended for liquids, while specific models are designed for certain solid materials. Pobel offers both configurations.

What Is the Difference Between a Pycnometer and a Hydrometer?

A pycnometer uses the relationship between mass and a known volume, while a traditional glass hydrometer measures by flotation.

What Pycnometer Capacities Are Available?

It depends on the model. For example, Pobel’s Gay-Lussac pycnometers are available in capacities of 5, 10, 25, 50 and 100 ml, while models for solids are available in capacities of 500, 1000 and 2000 ml.

Can Calibrated Pycnometers Be Purchased?

Yes. Pobel offers certain calibrated Gay-Lussac models supplied with an individual certificate.

What Is a Gay-Lussac Pycnometer?

It is a type of pycnometer used for density determination that incorporates a capillary stopper. Pobel offers calibrated and uncalibrated models, as well as versions incorporating a thermometer.

Find the Right Pycnometer for Your Laboratory

Explore our range of laboratory pycnometers and select the design, capacity and configuration that best suit your sample type and the procedure you need to carry out. If you are unsure which model to choose, contact the Pobel team for advice.