🧪 Bromine number of petroleum distillates (electrometric titration)
In short
Determination of the bromine number (grams of bromine reacting with 100 g of sample) of petroleum distillates and commercial aliphatic olefins by titration with a bromide-bromate solution with electrometric end-point detection. The test is performed according to ASTM D1159-23; Quantity: bromine number — grams of bromine (Br₂) reacting with 100 g of sample. The procedure comprises 5 steps; it is used for: Bromine number of petrol, kerosine and distillates in the gas oil range (90 % distillation point under 327 °C), Commercial aliphatic olefins with a bromine number from 95 to 165 — supporting evidence of purity and identity, Estimation of the percentage of olefins in distillates boiling up to approximately 315 °C with the procedure of Annex A2.
At a glance
- Standard: ASTM D1159-23
- Category: Petrochemistry
- Procedure steps: 5
- Quantity: bromine number — grams of bromine (Br₂) reacting with 100 g of sample
- Petroleum distillates: 90 % distillation point (ASTM D86) under 205 °C: bromine number at most 175; 205–327 °C: at most 10
- Commercial olefins: bromine number from 95 to 165; the method is not suitable for normal alpha-olefins
Overview
STATUS (as of 06.11.2026). The current edition in the ASTM store is ASTM D1159-23; ASTM D1159-07(2017), given in this description until now, is a historical edition. The American standard has not been adopted into the PN collection. We did not have the full text — the scope and significance come from the standard's page in the ASTM store, and the procedure from two application notes based on ASTM D1159 (Hach, note DOC316.52.93103 "based on ASTM D1159-07 (2012)" of 2015, and SI Analytics); details from the notes are given as coming from them, not from the standard. The previous name of the entry referred to the olefin content of fuels, which this standard does not determine — it has been changed to the name of its subject; the page address is unchanged.
SCOPE (ASTM D1159, Section 1). The method covers the bromine number of: petroleum distillates substantially free of material lighter than isobutane, with a 90 % distillation point (according to ASTM D86) under 327 °C — in practice petrol (including leaded, unleaded and oxygenated fuels), kerosine and distillates in the gas oil range, where for a 90 % distillation point under 205 °C the bromine number is at most 175 and for 205–327 °C at most 10; and commercial olefins — mixtures of aliphatic mono-olefins with a bromine number from 95 to 165 (e.g. propylene trimer and tetramer, butene dimer, mixed nonenes, octenes and heptenes). The method is not suitable for normal alpha-olefins. With a bromine number below 1.0 a more precise result is given by ASTM D2710, and below 0.5 ASTM D2710 or the bromine index methods for aromatic hydrocarbons (ASTM D1492, D5776) must be used.
SIGNIFICANCE (ASTM D1159, Section 5). The bromine number is a measure of aliphatic unsaturation in petroleum samples; together with the calculation procedure of Annex A2 it can be used to estimate the percentage of olefins in distillates boiling up to approximately 315 °C. The magnitude of the bromine number indicates the quantity of bromine-reactive constituents, not their identity, so without the study described in Annex A1 it should not be used as a measure of olefinic unsaturation. In commercial mono-olefins the bromine number provides supporting evidence of purity and identity.
OLEFIN CONTENT OF PETROL — METHODS SPECIFIED BY REGULATION. The regulation on quality requirements for liquid fuels (Journal of Laws 2024 item 1018, Annexes 1 and 2, item 11) allows at most 18.0 % (V/V) of olefins in motor petrol. The regulation on test methods for liquid fuels (Journal of Laws 2024 item 1058, Part I point 10) specifies for this determination fluorescent indicator adsorption (PN-EN 15553) or multidimensional gas chromatography (PN-EN ISO 22854) — not the bromine number.
WHAT WE DO NOT GIVE HERE. Without the text of the standard we do not give the requirements for the apparatus, polarization voltage and end-point criterion, calculation formulae, the procedure of Annexes A1–A2 or the precision. We have removed statements without a source or contradicting the sources: the advantage over the FIA method, the molar mass of "hexene" for conversions, the effect of olefins on the octane number and deposits, and "bromine in acetic acid" as the titrant (the titrant is an aqueous solution of potassium bromide and potassium bromate).
Method principle
Bromine reacts with C=C double bonds by addition. According to the application notes based on ASTM D1159 the titrant is a solution of potassium bromide and potassium bromate, from which bromine is formed in the acidified titration solvent (5 Br⁻ + BrO₃⁻ + 6 H⁺ → 3 Br₂ + 3 H₂O). The dissolved sample is titrated at a temperature of 0 °C to 5 °C, and the end point is detected electrometrically with a pair of platinum electrodes with an imposed polarization current (Hach note: potentiometry with imposed current). The bromine number is expressed in grams of bromine (Br₂) per 100 g of sample; the percentage of olefins can be estimated from it only with the procedure of Annex A2 of the standard.
Applications
- Bromine number of petrol, kerosine and distillates in the gas oil range (90 % distillation point under 327 °C)
- Commercial aliphatic olefins with a bromine number from 95 to 165 — supporting evidence of purity and identity
- Estimation of the percentage of olefins in distillates boiling up to approximately 315 °C with the procedure of Annex A2
Key parameters
| Parameter | Value |
|---|---|
| Quantity | bromine number — grams of bromine (Br₂) reacting with 100 g of sample |
| Petroleum distillates | 90 % distillation point (ASTM D86) under 205 °C: bromine number at most 175; 205–327 °C: at most 10 |
| Commercial olefins | bromine number from 95 to 165; the method is not suitable for normal alpha-olefins |
| Low bromine number | below 1.0 — ASTM D2710 is more precise; below 0.5 — ASTM D2710 or ASTM D1492, D5776 |
| Titration temperature (application notes) | from 0 °C to 5 °C |
| Titrant (application notes) | potassium bromide-bromate solution 0.25 mol/l as Br₂ |
Standard
- Standard number
- ASTM D1159-23
- Title (PL)
- Liczba bromowa destylatów naftowych i handlowych olefin alifatycznych metodą miareczkowania elektrometrycznego
- Title (EN)
- Standard Test Method for Bromine Numbers of Petroleum Distillates and Commercial Aliphatic Olefins by Electrometric Titration
Step-by-step procedure
-
Checking the scope
Establish whether the sample is within the scope of the standard (distillate with a 90 % distillation point under 327 °C or a commercial olefin with a bromine number of 95–165). With a bromine number below 1.0 consider ASTM D2710.
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Preparing the solutions
According to the application notes: prepare the bromide-bromate titrant and the titration solvent (acetic acid, methanol, chlorinated solvent, sulfuric acid (1+5)); the titrant concentration can be checked iodometrically with sodium thiosulfate.
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Preparing the sample
According to the application notes: dissolve the weighed sample (mass depending on the expected bromine number — table in the notes) in a 50 ml volumetric flask in the chlorinated solvent and transfer a 5 ml aliquot to 110 ml of titration solvent.
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Titration
Cool the solution to 0 °C to 5 °C and titrate with the bromide-bromate titrant with electrometric end-point detection. Also carry out a blank titration.
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Result
Calculate the bromine number in grams of Br₂ per 100 g of sample using the formula of the standard. To estimate the percentage of olefins, use only the procedure of Annex A2 and the study of Annex A1.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Titrator with electrometric detection | Pair of platinum electrodes for titration with polarization (application notes) | — |
| Jacketed titration vessel and thermostat | Keeping the solution at a temperature of 0 °C to 5 °C (application notes) | — |
| 50 ml volumetric flask, pipette and magnetic stirrer | Dissolving the weighed sample and taking an aliquot for titration (application notes) | — |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Potassium bromate | 7758-01-2 | Component of the bromide-bromate titrant (notes: 13.92 g KBrO₃ and 51.0 g KBr in 1 l of water) |
| Potassium bromide | 7758-02-3 | Component of the bromide-bromate titrant |
| Glacial acetic acid | 64-19-7 | Main component of the titration solvent (notes: 714 ml acetic acid, 134 ml methanol, 134 ml chlorinated solvent and 18 ml sulfuric acid (1+5) per 1 l) |
| Methanol | 67-56-1 | Component of the titration solvent (application notes) |
| 1,1,1-Trichloroethane or dichloromethane | 71-55-6 | Sample solvent and component of the titration solvent; the notes give dichloromethane (CAS 75-09-2) as a replacement for 1,1,1-trichloroethane |
| Sulfuric acid (1+5) | 7664-93-9 | Acidification of the titration solvent (application notes) |
| Sodium thiosulfate 0.1 mol/l and potassium iodide | 7772-98-7 | For checking the titrant concentration (application notes; KI 150 g/l, CAS 7681-11-0) |
Health and safety (OHS)
- Potassium bromate (harmonised CLP classification): may cause fire or explosion, strong oxidizer (H271), toxic if swallowed (H301), may cause cancer (H350)
- Bromine formed in the solution (CLP): causes severe skin burns and eye damage (H314), fatal if inhaled (H330), very toxic to aquatic life (H400)
- Glacial acetic acid (CLP): flammable (H226), causes severe skin burns and eye damage (H314)
- Methanol (CLP): highly flammable (H225), toxic if swallowed, in contact with skin and if inhaled (H301, H311, H331), causes damage to organs (H370)
- Dichloromethane (CLP): suspected of causing cancer (H351)
- 1,1,1-Trichloroethane (CLP): harmful if inhaled (H332), harms public health and the environment by destroying ozone in the upper atmosphere (H420)
- Sulfuric acid (CLP): causes severe skin burns and eye damage (H314)
Frequently asked questions
Which standard describes this test?
The test is performed according to ASTM D1159-23 — “Standard Test Method for Bromine Numbers of Petroleum Distillates and Commercial Aliphatic Olefins by Electrometric Titration”.
How does this method work?
Bromine reacts with C=C double bonds by addition. According to the application notes based on ASTM D1159 the titrant is a solution of potassium bromide and potassium bromate, from which bromine is formed in the acidified titration solvent (5 Br⁻ + BrO₃⁻ + 6 H⁺ → 3 Br₂ + 3 H₂O).
What is the measuring range and accuracy?
Quantity: bromine number — grams of bromine (Br₂) reacting with 100 g of sample; Petroleum distillates: 90 % distillation point (ASTM D86) under 205 °C: bromine number at most 175; 205–327 °C: at most 10; Commercial olefins: bromine number from 95 to 165; the method is not suitable for normal alpha-olefins; Low bromine number: below 1.0 — ASTM D2710 is more precise; below 0.5 — ASTM D2710 or ASTM D1492, D5776.
How long does the test take?
The procedure comprises 5 steps. The standard does not give a duration for every stage — the laboratory's own procedure decides.
What equipment is required?
Titrator with electrometric detection, Jacketed titration vessel and thermostat, 50 ml volumetric flask, pipette and magnetic stirrer.
Where is this test used?
Bromine number of petrol, kerosine and distillates in the gas oil range (90 % distillation point under 327 °C); Commercial aliphatic olefins with a bromine number from 95 to 165 — supporting evidence of purity and identity; Estimation of the percentage of olefins in distillates boiling up to approximately 315 °C with the procedure of Annex A2.
What safety precautions apply?
Potassium bromate (harmonised CLP classification): may cause fire or explosion, strong oxidizer (H271), toxic if swallowed (H301), may cause cancer (H350); Bromine formed in the solution (CLP): causes severe skin burns and eye damage (H314), fatal if inhaled (H330), very toxic to aquatic life (H400); Glacial acetic acid (CLP): flammable (H226), causes severe skin burns and eye damage (H314); Methanol (CLP): highly flammable (H225), toxic if swallowed, in contact with skin and if inhaled (H301, H311, H331), causes damage to organs (H370); Dichloromethane (CLP): suspected of causing cancer (H351); 1,1,1-Trichloroethane (CLP): harmful if inhaled (H332), harms public health and the environment by destroying ozone in the upper atmosphere (H420); Sulfuric acid (CLP): causes severe skin burns and eye damage (H314).
Which laboratory can perform this test?
The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number ASTM D 1159.