Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D2379-09 – Standard Test Method Technical Guide
📖 Scope, Significance, and Referenced Documents
ASTM D2379 – 09 (Reapproved 2023) provides a standardized test method for determining the acidity of commercially available formaldehyde solutions. This test method is under the jurisdiction of ASTM Committee D01 and is essential for specification acceptance in various industrial applications involving solvents, plasticizers, and chemical intermediates.
The scope specifies that the values stated in SI units are to be regarded as standard. Test results must be rounded off “to the nearest unit” in the last right-hand digit of the specification limit, in accordance with Practice E29. Safety is emphasized, directing users to the supplier’s Safety Data Sheet (SDS) for hazard information, with specific hazard statements detailed in Section 7 of the standard. This international standard was developed in accordance with internationally recognized principles on standardization established by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
⚠️ Safety Notice: This standard does not purport to address all of the safety concerns associated with its use. It is the responsibility of the user to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Always consult the supplier’s Safety Data Sheet (SDS) as directed in Sections 1.4 and 1.5.
⚗️ Apparatus and Reagent Specifications
The test method involves a straightforward acid-base titration. A specimen of the formaldehyde solution is titrated with a standard alkali solution to the visual endpoint indicated by bromthymol blue. The following apparatus and reagents are specifically called out in the standard.
| 🔬 Component | 📋 Specification / Preparation Details |
|---|---|
| Buret | 25 mL capacity, calibrated in 0.1 mL divisions, fitted with a TFE-fluorocarbon resin stopcock. |
| Reagent Water | Must conform to Type IV or better of ASTM Specification D1193. |
| Bromthymol Blue Indicator Solution | 1.0 g/L solution. Prepared by dissolving 0.1 g of the water-soluble form of bromthymol blue indicator powder in 100 mL of water. |
| Sodium Hydroxide (NaOH) Solution | Standard solution of 0.1 N, prepared and standardized according to ASTM Practice E200. |
| General Reagent Chemicals | Reagent grade chemicals conforming to the specifications of the ACS Committee on Analytical Reagents shall be used unless otherwise indicated. |
💡 Technical Tip: For accurate and reproducible results, ensure the standardized 0.1 N NaOH solution is free of carbonate. Practice E200 provides comprehensive guidelines on the preparation, standardization, and storage of this solution. The visual change from yellow (acidic) to blue (basic) defines the endpoint of the titration.
📈 Procedure Summary and Reporting of Results
According to Section 4 of the standard, the significance of this test method is to provide a measurement of acidity (calculated as formic acid) in formaldehyde solutions, which is critical for specification acceptance. The summary of the method, given in Section 3, states that a specimen is simply titrated with the standard alkali to the bromthymol blue end point.
The calculation of the acidity involves the volume of NaOH titrant used, its exact normality, the specimen weight or volume, and the milliequivalent weight of formic acid. For purposes of determining conformance, the final reported result must conform to the rounding-off methods prescribed in ASTM Practice E29, which dictates that observed or calculated values be rounded “to the nearest unit” in the last right-hand digit of the specification limit.
❓ Frequently Asked Questions
🔍 What is the fundamental principle of this test method?
As stated in Section 3.1, the test method operates on the principle of an acid-base titration. A specimen of formaldehyde solution is titrated with a standard alkali solution (0.1 N NaOH) to the visual endpoint of the bromthymol blue indicator.
💡 What specific analyte does this method measure?
According to Section 4.1, this test method provides a measurement of acidity. The result is calculated and expressed specifically as formic acid (HCOOH), which is the primary acidic species found in aged or oxidized formaldehyde solutions.
⚡ What is the quality requirement for the water used in this test?
Section 6.2 of the standard specifies that all references to water mean reagent water conforming to the requirements of Type IV or better, as defined in ASTM Specification D1193.
📌 Which ASTM standards are referenced as integral to this test method?
Section 2.1 references key ASTM standards including: D1193 (Specification for Reagent Water), D2380 (Test Method for Methanol Content of Formaldehyde Solutions), E29 (Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications), and E200 (Practice for Preparation, Standardization, and Storage of Standard and Reagent Solutions for Chemical Analysis).