AATCC 149-2018 Chelation Value of Aminopolycarboxylic Acids and Their Salts: Calcium Oxalate Method.
1.1 The active content of ethylenediaminetetraacetic acid (EDTA), N-hy- droxyethylethylenediaminetriacetic acid (HEDTA) and diethylenetriaminepenta- acetic acid (DTPA) and their salts is usually expressed by the calcium chelation value (CaCV). This value indicates the amount of calcium (as calcium carbon- ate) which will be chelated by a known weight of chelating agent.
2. Principle
2.1 The chelation value is determined experimentally by titrating a weighed sample of chelating agent with a calcium ion solution of known concentration. A precipitating anion (oxalate) is present during the titration. As the calcium solu- tion is added, the ions are chelated by the chelating agent and no permanent precip- itate is formed as long as there is free chelating agent present. Beyond this point, any excess calcium ion that is added reacts with oxalate anion to form a cloudy precipitate which is the endpoint.
2.2 The CaCV indicates the amount of calcium (as calcium carbonate) that will be sequestered by a known weight of chelating agent and is expressed as milli- grams of calcium carbonate (CaCO 3 ) per gram of chelating agent (mg calcium carbonate/g chelating agent).
3. Terminology
3.1 chelating agent, n.—in textile chemistry, a chemical capable of deactivat- ing metal ions by formation of a water-soluble complex. SYN.—sequestering agent.
4. Safety Precautions NOTE: These safety precautions are for information purposes only. The precautions are ancillary to the testing proce- dures and are not intended to be all inclu- sive. It is the user’s responsibility to use safe and proper techniques in handling materials in this test method. Manufacturers MUST be consulted for specific details such as material safety data sheets and other manufacturer’s recommenda- tions. All OSHA standards and rules must also be consulted and followed.
4.1 Good laboratory practices should be followed. Wear safety glasses in all laboratory areas.
4.2 All chemicals should be handled with care.
4.3 In preparing, dispensing and han- dling hydrochloric acid and sodium hydroxide use chemical goggles or face shield, impervious gloves and an imper- vious apron. Concentrated acids should be handled only in an adequately ventilated laboratory hood. CAUTION: Always add acid to water.
4.4 Diethylamine hydrochloride is an eye, skin and respiratory irritant. It should be handled only in an adequately ventilated hood.
4.5 An eyewash/safety shower should be located nearby and a self-contained breathing apparatus should be readily available for emergency use.
4.6 Exposure to chemicals used in this procedure must be controlled at or below levels set by governmental authorities (e.g., Occupational Safety and Health Administration’s [OSHA] permissible ex- posure limits [PEL] as found in 29 CFR 1910.1000; see www.osha.gov for latest version). In addition, the American Con- ference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Val- ues (TLVs) comprised of time weighted averages (TLV-TWA), short term exposure limits (TLV-STEL) and ceiling lim- its (TLV-C) are recommended as a gen- eral guide for air contaminant exposure which should be met (see 15.1).AATCC 149 pdf download.