⚖️ Density of Fuels and Oils

Petrochemistry PN-EN ISO 12185

Overview

STATUS (as of 30.10.2026). PN-EN ISO 12185:2024-08 — Polish and English versions, implements EN ISO 12185:2024 and ISO 12185:2024 [IDT]; the Polish version was published on 21.01.2026. It replaced PN-EN ISO 12185:2002 (implementing ISO 12185:1996), which the PKN catalogue marks as withdrawn and replaced. ISO 12185:2024 is the second edition of the standard, published on 15.03.2024.

SCOPE (clause 1). Density of crude petroleum and related products in the range from 600 kg/m³ to 1 100 kg/m³, measured with a laboratory oscillating U-tube density meter — for liquids that can be handled as single-phase liquids at the test temperature and pressure. The method covers liquids of any vapour pressure, provided that precautions are taken to keep them in a single phase: loss of light components changes the density both during sample handling and during the determination. It is not intended for in-line density meters. According to the corresponding American standard ASTM D4052 (5.2), determining density is necessary for converting measured volumes of petroleum and its products to volumes at the standard temperature of 15 °C.

EDITION (foreword and introduction). The second edition replaced ISO 12185:1996 and incorporates its Technical Corrigendum Cor 1:2001; definitions (clause 3) and quality control checks of the meter (9.5) have been added. The first edition was written when there were few models of such density meters on the market; today instruments of different manufacturers correct the effect of viscosity on the displayed density with different methods and algorithms, so the new edition covers a wider range of instruments and gives requirements for the apparatus and its preparation (clauses 5 and 9, Annex A).

STRUCTURE OF THE STANDARD (table of contents). Apparatus: density meter, homogenizer, constant-temperature bath; reagents: flushing solvent and adjustment liquids; sampling and sample preparation; apparatus preparation: test temperature, cell cleaning, verification and adjustment, calibration, quality control checks; test procedure, calculation, test report and precision (repeatability, reproducibility); informative Annex A on meter calibration.

HOW THE TEST PROCEEDS — ACCORDING TO THE 1996 EDITION (ISO 12185:1996 with Corrigendum 1:2001; we do not know the content of clauses 5–13 of the current edition). A small portion of the sample (typically less than 1 ml) is introduced into a temperature-controlled cell; the density is calculated from the oscillation frequency and from cell constants determined beforehand with calibration fluids of known density — at least two, whose densities bracket the density of the sample (water and air are allowed). The density meter has a resolution of 0.1 kg/m³ or better; the standard warned that the viscosity of the sample can shift the result by up to 1 kg/m³ (check with a pyknometer or with standards of similar viscosity). The sample is not cooled below its cloud point, its wax appearance temperature (WAT) or below 20 °C above its pour point; waxy crude oil and distillates are warmed to 3 °C above the WAT or the cloud point before mixing. The density is determined at the reference temperature (15 °C or 20 °C) wherever possible. Calibration — on installation, when the test temperature is changed and after the apparatus has been disturbed; verification — not more than 7 days before use; before the measurement the reading with the cell filled with air must agree with the value from the calibration within ±1 of the last digit. Samples with light ends are not drawn in by suction; the cell is inspected for bubbles, and for viscous liquids a short overpressure reveals gas bubbles by a large change of the reading. The reading is recorded when it is steady within 0.1 kg/m³, together with the cell temperature to the nearest 0.1 °C; conversion to the reference temperature — according to ISO 91-1 (15 °C) or ISO 91-2 (20 °C) after the correction from Annex A. Result: to the nearest 0.1 kg/m³ at the reference temperature.

WHAT WE DO NOT GIVE HERE. The requirements of the current edition for the density meter and the way of correcting the effect of viscosity (clause 5, Annex A), the rules for verification, adjustment and quality control checks (9.3–9.5), the course of the determination (clause 10) or the current repeatability and reproducibility values (clause 13) — we only know the titles of these clauses; we do not carry over the precision values of the 1996 edition.

Method principle

A small portion of the sample is introduced into a temperature-controlled U-tube measuring cell. The density meter measures the oscillation frequency of the cell, and the density is calculated from cell constants determined beforehand by measuring the oscillation of the cell filled with calibration fluids of known density.

The result is valid when the sample in the cell remains single-phase — without gas bubbles and without loss of light components. The density is reported at the reference temperature; a result obtained at another temperature is converted (1996 edition: according to ISO 91-1 for 15 °C or ISO 91-2 for 20 °C).

Applications

• Crude petroleum, petroleum products and related products with a density from 600 to 1 100 kg/m³ (clause 1)
• Liquids of any vapour pressure — provided they are kept in a single phase without loss of light components (clause 1)
• Diesel fuel — requirement of the Polish regulation on quality requirements for liquid fuels: density at 15 °C from 820.0 kg/m³ in the summer period (815.0 kg/m³ in the transitional and winter periods) to 845.0 kg/m³, for diesel with improved low-temperature properties 800.0–840.0 kg/m³ (Dz.U. 2024 item 1018, Annex 3 No 3)
• Motor petrol — density at 15 °C 720.0–775.0 kg/m³ (Dz.U. 2024 item 1018, Annex 1 No 4)
• Input data for calculating the cetane index according to PN-EN ISO 4264 — density at 15 °C to the nearest 0.1 kg/m³ (ISO 4264:2018, 5.1)

Key parameters

Standard

Standard number

PN-EN ISO 12185:2024-08

Title (PL)

Ropa naftowa, przetwory naftowe i produkty podobne — Oznaczanie gęstości — Gęstościomierz laboratoryjny z czujnikiem oscylacyjnym typu U-rurki

Title (EN)

Crude petroleum, petroleum products and related products — Determination of density — Laboratory density meter with an oscillating U-tube sensor

Step-by-step procedure

1. Test temperature

   The density is determined at the reference temperature wherever possible (9.1). 1996 edition: otherwise at least 3 °C above the cloud point or WAT or 20 °C above the pour point, and below the temperature at which gas appears in the sample.

2. Preparing and verifying the apparatus

   Cell cleaning, verification and adjustment, calibration and quality control checks — 9.2–9.5. 1996 edition: calibration on installation, on a change of test temperature and after disturbance; verification not more than 7 days before use; reading with air in agreement with the calibration within ±1 of the last digit.

3. Preparing the sample

   Clauses 7–8. 1996 edition: without loss of light ends and without cooling below the cloud point, the WAT or 20 °C above the pour point; samples containing water or sediment are mixed in the original container.

4. Introducing the sample and reading

   Clause 10. 1996 edition: the cell is filled with a syringe or autosampler according to the manufacturer’s instructions, checked for bubbles (the cell illumination is switched off immediately after the check), and the reading is recorded when it is steady within 0.1 kg/m³, with the cell temperature to the nearest 0.1 °C.

5. Calculation and result

   Clause 11. 1996 edition: conversion to the reference temperature according to ISO 91-1 (15 °C) or ISO 91-2 (20 °C) after the correction from Annex A; result to the nearest 0.1 kg/m³.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• The standard does not address all hazards associated with its use — safety measures are established by the user (warning of the standard)
• Ammonium peroxydisulfate in concentrated sulfuric acid is a strong oxidizing agent (1996 edition, warning to 6.2)

Frequently asked questions