Relative Density Bottle (Specific Gravity Bottle)

Quick Answer: A Relative Density Bottle, also called a Specific Gravity Bottle or pyknometer, is a precision-ground borosilicate glass vessel used to measure the density and relative density (specific gravity) of liquids by comparing the weight of a fixed volume of sample against an equal volume of water. It is a standard item in chemistry, pharmaceutical, and quality-control laboratories.

Description

The Relative Density Bottle from LabEquip is manufactured from chemically resistant borosilicate 3.3 glass and fitted with a close-fitting, interchangeable ground-glass stopper that carries a fine capillary bore. This capillary allows excess liquid to escape when the stopper is inserted, ensuring the vessel is filled to a precisely repeatable internal volume every time it is used — the key requirement for accurate relative density determination. The stopper is individually ground to its own bottle, so each unit is matched as a set and should not be interchanged with stoppers from other bottles.

In use, the bottle is weighed empty, then filled with distilled water and weighed again, and finally filled with the test liquid and weighed a third time. Comparing these readings gives the relative density of the sample against water at a stated temperature. Because the glass is dimensionally stable and resistant to thermal shock, results remain consistent across repeated determinations, which is essential for pharmacopoeial and industrial testing protocols.

These bottles are supplied in a range of standard laboratory capacities to suit different sample sizes and testing methods — confirm the exact volume required for your application at the time of enquiry.

Specifications

Applications

• Determining relative density (specific gravity) of liquids in chemistry teaching and research laboratories
• Pharmaceutical quality-control testing of syrups, solvents, and formulations
• Density checks on oils, fuels, and petrochemical samples
• Beverage and food-testing laboratories checking syrup or liquid concentration
• Calibration verification exercises in analytical chemistry courses

Care & Handling

• Always keep the ground-glass stopper matched to its own bottle; do not swap stoppers between units as the ground fit is unique to each pair.
• Clean thoroughly with a suitable laboratory detergent and rinse with distilled water before and after each determination to avoid contaminating results.
• Dry the bottle and stopper carefully, ensuring the capillary bore is clear, before storage.
• Handle the ground-glass joint gently — avoid dropping or knocking the stopper against the neck, which can chip the precision-ground surface.
• Store upright in a dry cabinet, away from other glassware that could chip the stopper or neck on contact.

Why Choose LabEquip

LabEquip supplies borosilicate laboratory glassware, including relative density bottles, alongside a broader range of lab glassware and general chemistry lab equipment for schools, colleges, and industrial laboratories. Each item is checked before dispatch, and our team can help you confirm the right capacity and specification for your testing method. For bulk orders, institutional procurement, or technical questions about this product, please contact us and our team will assist promptly.

Frequently Asked Questions

What is a relative density bottle used for?

A relative density bottle, or pyknometer, is used to measure the density of a liquid and its relative density (specific gravity) compared with water, by weighing a precisely fixed volume of the sample.

How does the ground-glass stopper ensure accurate results?

The stopper has a fine capillary bore that lets excess liquid escape as it is inserted, so the bottle always holds the same internal volume of liquid, making repeated weighings comparable and accurate.

Can stoppers be interchanged between different relative density bottles?

No. Each stopper is individually ground to fit its own bottle precisely, so stoppers should never be swapped between different units, as this can affect the sealed volume and the accuracy of results.

What material is the relative density bottle made from?

It is made from borosilicate 3.3 glass, chosen for its chemical resistance, dimensional stability, and resistance to thermal shock, which help keep density measurements consistent over repeated use.

What capacity does the relative density bottle come in?

These bottles are supplied in a range of standard laboratory capacities. Please confirm the exact volume you require for your test method when you enquire, and our team will help you select the right size.

How should a relative density bottle be cleaned and stored?

Clean it with a suitable laboratory detergent, rinse with distilled water, and dry carefully including the capillary bore. Store the bottle and its matched stopper together, upright, in a dry cabinet away from other glassware.

Last Updated: September 2026