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D5776-21 – Standard Test Method Technical Guide
🧪 Introduction and Scope of D5776-21
The ASTM D5776-21 standard formally establishes a procedure for determining the Bromine Index (BI) of aromatic hydrocarbons using electrometric titration. The Bromine Index, defined in Section 3.1.1 of the standard, is the number of milligrams of bromine consumed by 100 g of sample under the given test conditions. This value serves as a critical measure for quantifying trace amounts of unsaturated compounds (olefins) in aromatic hydrocarbons.
The scope of this test method is specifically defined. It is applicable to aromatic hydrocarbons containing no more than trace amounts of olefins, that are substantially free from material lighter than isobutane, and which have a distillation end point under 288 °C. The standard provides detailed precision data for materials having a bromine index below 35.
⚠️ Precision Limitation: This test method is applicable to materials having bromine indexes below 35. Materials with a higher bromine index can be analyzed by this method; however, the precision section does not apply. Analysts must exercise caution when interpreting results outside this validated range.