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D2083-92 – Standard Test Method Technical Guide
📐 Understanding the Calculation Method for Fatty Amines
ASTM D2083-92 provides a standardized computational approach for determining the percentages of primary, secondary, and tertiary amines in fatty amine samples. This method is specifically designed for materials containing only fatty primary amines, difatty secondary amines, trifatty tertiary amines, and non-amines. It relies on experimental data obtained from potentiometric or indicator titration methods and a separate non-amine content test. The calculations assume that the alkyl chain lengths in the mono-, di-, and trifatty amines are the same average length, ensuring consistency in the derived molecular weight.
📌 Important Note on Applicability: This test method is not applicable to blends such as a mixture of coco primary amine and tallow difatty secondary amine. It is strictly for systems containing only single fatty amine types and non-amines.
⚙️ Data Requirements and Calculation Procedure
To perform the calculations, the user must first determine the primary, secondary, and tertiary amine values (PAV, SAV, TAV) using either Test Methods D 2073 (Referee Potentiometric Method) or D 2074 (Alternative Indicator Method). Additionally, the percent non-amines (PNA) must be obtained via Test Method D 2082. These values are then used in the equations below to compute the composition.
| 🔢 Variable | 📏 Definition |
|---|---|
| X | Average molecular weight of the primary amine |
| PAV | Primary amine value of the sample |
| SAV | Secondary amine value of the sample |
| TAV | Tertiary amine value of the sample |
| PNA | Percent non-amine in the sample |
| ⚙️ Calculation | 📐 Formula |
|---|---|
| Average molecular weight (X) | X = [561(100 – PNA) + 17(SAV) + 34(TAV)] / [PAV + 2(SAV) + 3(TAV)] |
| Primary amine, % | Primary % = PAV × X / 561 |
| Secondary amine, % | Secondary % = SAV × (2X – 17) / 561 |
| Tertiary amine, % | Tertiary % = TAV × (3X – 34) / 561 |
⚡ Precision Note: Precision and bias were not established when this method was written. The standard has been in use for many years and its usefulness is well established, but future revisions may include precision data.
📊 Key Assumptions and Practical Use
The calculation hinges on the assumption that the average molecular weight of the primary amine (X) can be derived from the experimental values. This derived X is then used to compute each amine type’s percentage. The method is widely used in the fatty amine industry for quality control and product characterization, particularly for analyzing tallow, coco, or similar fatty amine derivatives.
❓ Frequently Asked Questions
🔍 What is the scope of ASTM D2083?
This method covers calculation of primary, secondary, and tertiary amine percentages in materials containing only those amines plus non-amines. It is not intended for complex blends of different fatty amine types.
💡 How are the amine values obtained for this calculation?
The primary, secondary, and tertiary amine values must be determined using Test Methods D 2073 (potentiometric) or D 2074 (indicator method), while the non-amine content is determined per Test Method D 2082.
⚡ Can this method be applied to fatty amine blends?
No. The method is explicitly not applicable to blends such as a mixture of coco primary amine and tallow difatty secondary amine. It requires samples consisting only of single types of each amine.
📌 What assumption underlies the calculation formulas?
The equations assume that the alkyl chain lengths in the mono-, di-, and trifatty amines are the same average length, which is critical for the derived molecular weight (X) to be valid.