🧫 Water content — xylene distillation method

Petrochemistry ASTM D 95

Overview

STATUS (as of 06.11.2026). The current edition in the ASTM store is ASTM D95-23ε1 (editorial correction of the 2023 edition); ASTM D95-13(2018), 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 of the 2023 edition — the description is based on the scope and significance of the method from the standard's page in the ASTM store; the distillation procedure, apparatus and solvents are given according to ISO 3733:1999 (in Poland PN-ISO 3733 — a separate Knowledge Base entry), a standard on the same subject with the same principle, and not according to the text of ASTM D95.

SCOPE (ASTM D95, Section 1). The method covers the determination of water in the range from 0 % to 25 % by volume in petroleum products, tars and other bituminous materials by the distillation method. Volatile water-soluble material, if present, may be measured as water. The products considered during the development of the method are listed in Table 1 of the standard. For bituminous emulsions the standard refers to ASTM D244 and for crude oils to ASTM D4006 (API MPMS Chapter 10.2); with some types of oil satisfactory results may be obtained with the centrifuge method ASTM D1796.

SIGNIFICANCE (ASTM D95, Section 5). Knowledge of the water content is important in the refining, purchase, sale and transfer of products. The amount of water determined by this method (to the nearest 0.05 % or 0.1 % by volume, depending on the trap used) may be used to correct the volume in the custody transfer of petroleum products and bituminous materials, and the allowable water content may be specified in contracts.

WHAT WE DO NOT GIVE HERE. Without the text of ASTM D95 we do not give its requirements for the apparatus, solvents, distillation rate, precision or calculation of the result — the figures in the fields below come from ISO 3733:1999 and are marked as such. We have also removed figures and assessments without a source: step times, the "detection threshold of 0.02 %", the boiling temperature of the azeotrope, the comparison with the Karl Fischer method, the year of the first edition of the standard and the list of effects of water in fuels.

Method principle

The sample is heated under reflux with a water-immiscible solvent, which distils together with the water. The condensate separates in the trap: the water settles in its graduated section and the solvent returns to the still. The volume of water collected is read and reported as a percentage by volume of the sample. This is how ISO 3733:1999 describes the principle; the scope of ASTM D95 covers water from 0 % to 25 % by volume and the result — according to Section 5 of ASTM D95 — is accurate to 0.05 % or 0.1 % by volume, depending on the size of the trap.

Applications

• Petroleum products, tars and other bituminous materials — water from 0 % to 25 % by volume
• Volume correction in the custody transfer of petroleum products and bituminous materials
• Checking the allowable water content specified in contracts
• Refining, purchase and sale of petroleum products

Key parameters

Standard

Standard number

ASTM D95-23ε1

Title (PL)

Zawartość wody w produktach naftowych i materiałach bitumicznych metodą destylacji

Title (EN)

Standard Test Method for Water in Petroleum Products and Bituminous Materials by Distillation

Step-by-step procedure

1. Choice of method

   Check whether the sample is within the scope of ASTM D95: petroleum products, tars and other bituminous materials, water from 0 % to 25 % by volume. Bituminous emulsions are tested according to ASTM D244 and crude oils according to ASTM D4006.

2. Checking the apparatus

   According to ISO 3733:1999: before first use verify the trap graduation with 0.05 ml increments of water, and before determinations carry out a recovery test with a known amount of water added to dry xylene.

3. Measuring the portion and solvent

   Choose the portion so that the water fits in the trap. According to ISO 3733:1999 liquid samples are measured with a cylinder, which is rinsed with solvent, and solid and viscous samples are weighed directly into the still with 100 ml of solvent chosen for the type of material.

4. Distillation

   Heat the still under reflux; the water collects in the graduated section of the trap and the solvent returns to the still. According to ISO 3733:1999 the condensate discharges at 2 to 9 drops per second, and distillation is ended when the volume of water remains constant for 5 min.

5. Reading and result

   After cooling, read the volume of water in the trap, subtract the solvent blank and report the water content in percent by volume to the nearest 0.05 % or 0.1 %, depending on the size of the trap.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• ASTM D95 contains a general statement that it does not address all safety concerns and that establishing safety practices is the responsibility of the user; specific hazard statements are in Section 6 of the standard (we did not have its content)
• Xylene (harmonised CLP classification): flammable liquid and vapour (H226), harmful in contact with skin and if inhaled (H312, H332), causes skin irritation (H315)
• Toluene (component of the solvent blend): highly flammable (H225), H304, H315, H336, suspected of damaging the unborn child (H361d), H373
• 2,2,4-Trimethylpentane (CLP): H225, H304, H315, H336, H400, H410

Frequently asked questions