Ethylenediaminetetraacetic acid (EDTA) has many scientific and medical uses. At the chemical level, it forms coordination compounds with metal ions, thus inactivating them. Biochemists use EDTA to inactivate enzymes, and inorganic chemists use it as a chemical buffer. Doctors use it to treat lead and calcium poisoning. It can also be used as preservative in processed foods and cosmetic products. Creating an EDTA solution can be tricky because it doesn't dissolve well at a pH of 7--the neutral pH of water. A strong base must be used in conjunction with water to create the solution.
- Deionized water, 1 liter
- Sodium hydroxide, solid, 20 g
- Large beaker, at least 1 liter
- Magnetic stirrer
The directions contained here will make a 0.5 Molar solution of EDTA with a pH near 8. Molarity is a measurement of the concentration of the solution. 0.5 Molar means that there is a half a mole of EDTA molecules in the 1 liter solution. One mole is equal to 6.022 x 10^23 molecules and is used as a standard unit of measurement in chemistry, much like bakers use the "dozen" as a unit.
Be sure to wear protective goggles, gloves and apron as you work with these chemicals.
Fill your large beaker to the 900 milliter (mL) mark with deionized water.
Use your balance to measure 186.1 g of EDTA and add it to the water in the beaker. Begin stirring the solution with the magnetic stirrer when you add the EDTA.
Use your balance to measure 20 g of sodium hydroxide (NaOH) and add roughly half of it to the solution. Continue stirring.
Add a gram or two more of NaOH every couple hours and watch the EDTA. It will start to dissolve into solution as the pH approaches 8. Once it has dissolved completely, add one more gram of NaOH to the solution and stop the stirrer.
Add enough water to the solution to fill the beaker the rest of the way to the 1-liter mark.