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D565-24 – Standard Test Method Technical Guide
🔬 Scope and Significance of ASTM D565-24
This standard test method, under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants, provides a definitive procedure for evaluating carbonizable substances in white mineral oil (Mineral Oil USP and Light Mineral Oil NF). It is the cornerstone test for determining conformance with the rigorous quality standards of the United States Pharmacopeia (USP), the National Formulary (NF), and the Food and Drug Administration (FDA). Originally approved in 1940, the standard has been meticulously updated, with the current edition published in November 2024, to ensure pharmaceutical mineral oils meet modern purity and safety expectations.
The method is straightforward yet chemically robust: the mineral oil sample is treated with concentrated sulfuric acid (H₂SO₄) under specifically defined conditions of volume, temperature, and agitation. The resulting color produced in the acid layer is then visually compared against a set of standardized reference colors. This simple colorimetric comparison effectively screens for the presence of unsaturated hydrocarbons and other readily carbonizable impurities, serving as a critical quality assurance measure for sensitive pharmaceutical and food-contact applications.
🧪 Apparatus Specifications and Reagent Requirements
The core apparatus is a meticulously specified test tube constructed from heat-resistant glass. The strict dimensional tolerances and calibration requirements are essential for ensuring the reproducibility and validity of the acid treatment procedure across different laboratories and operators.
| ⚙️ Parameter | 📐 Specification (per Section 6.1) |
|---|---|
| 🟦 Material | Heat-Resistant Glass |
| 🔢 Stopper | Well-ground glass matching numbers indestructibly marked on the tube |
| 📏 Overall Length | 140 mm ± 2 mm |
| 💠 Outside Diameter | 14.5 mm to 15.0 mm |
| 🎯 Primary Calibration | 5 mL level (accuracy ± 0.2 mL) |
| 🎯 Secondary Calibration | 10 mL level (accuracy ± 0.2 mL) |
| 🔬 Capacity (with stopper) | Between 23 mL and 26 mL |
⚡ Essential Safety Advisory: Concentrated sulfuric acid (H₂SO₄) is highly corrosive and reactive. Section 7 of the standard provides specific hazard statements. All users must strictly adhere to established safety, health, and environmental practices and wear appropriate personal protective equipment (PPE) when performing this test method.
Reagent water used in any ancillary or preparation procedures must conform to the purity requirements of ASTM Specification D1193 for Reagent Water. The test relies heavily on the stringent dimensional controls of the apparatus to ensure the precise 5 mL and 10 mL volumetric ratios of oil to acid are maintained, guaranteeing the test’s discriminatory power against carbonizable impurities.
📊 Compliance Framework and Regulatory References
ASTM D565-24 is deeply integrated into the pharmaceutical regulatory framework. The primary external standards and monographs that define the official acceptance criteria are the current editions of the USP and NF, alongside the FDA regulation 21 CFR 172.878. The method creates a direct, auditable link between the laboratory test result and the official compendial requirements.
| 🏛️ Authority | 📜 Specific Reference | 🎯 Application Scope |
|---|---|---|
| United States Pharmacopeia (USP) | Monograph on Mineral Oil | Pharmaceutical Grade White Mineral Oil |
| National Formulary (NF) | Monograph on Light Mineral Oil | Pharmaceutical Grade Light Mineral Oil |
| Food and Drug Admin. (FDA) | 21 CFR 172.878 | White Mineral Oil as Direct Food Additive |
| ASTM (Reference) | D1193 & D4175 | Reagent Water Spec. & Petroleum Terminology |
✅ Accreditable Unit Standards: The standard strictly specifies that values stated in SI units are to be regarded as the standard for the method. The only exception is for the dimension requirements of the color comparator shown in Fig. 1, which are provided in both SI and inch-pound units to maintain historical equipment compatibility while aligning with international standardization principles.
The outcome of the test is definitive. If the color of the acid layer is no darker than the prescribed reference standard, the mineral oil sample passes the test, confirming its suitability for use in pharmaceutical preparations. This single test, when performed correctly, provides a high level of confidence regarding the absence of objectionable levels of carbonizable substances.
❓ Frequently Asked Questions
🔍 What is the specific purpose of ASTM D565-24?
It determines if white mineral oil (Mineral Oil USP or Light Mineral Oil NF) contains carbonizable substances exceeding the limits defined by the USP, NF, and FDA regulations for pharmaceutical and food-grade applications.
⚡ What chemical reagent is critical to this test procedure?
Concentrated sulfuric acid (H₂SO₄). The mineral oil sample is vigorously treated with this acid under controlled conditions, and the resulting color of the acid extract serves as the direct indicator of carbonizable impurities.
💡 How is the result of the test interpreted?
The interpretation relies on a visual comparison. The color developed in the acid layer is compared against a specific reference standard. If the acid color is darker than the limit, the oil fails the test for carbonizable substances.
© 2026 TNLab — This article is a technical interpretation for reference only. The original standard as published by ASTM International takes precedence.