Eriochrome Black T (EBT) is a pivotal reagent for complexometric titrations and pH assessment in water studies. The following guide outlines a precise, laboratory‑grade preparation method that ensures reliable results and safety compliance.

Safety First

Before beginning, equip yourself with nitrile gloves and safety goggles. Work in a well‑ventilated area or under a fume hood, and keep all chemicals out of reach of children.

Required Materials

• Precision analytical balance (±0.1 mg)
• HiMedia Eriochrome Black T, Practical Grade (0.5 % w/v)
• HiMedia Hydroxylamine Hydrochloride, 10 % w/v (GRM1028‑100G)
• Belle Chemical Medical‑Grade Ethanol
• 100 mL volumetric beaker or glass container
• Glass stirring rod
• Glass dropper bottle or reagent bottle for storage

Preparation Procedure

1. Weigh the EBT: Place the empty beaker on the balance and tare it to zero. Transfer 0.5 g of EBT powder into the beaker with a clean spatula.

2. Add Hydroxylamine: Tare the balance again. Weigh out 2.0 g of hydroxylamine hydrochloride and add it to the beaker.

3. Dissolve the Powders: Add a small volume of ethanol (≈5 mL) to the beaker, then stir with the glass rod until the powders are fully dissolved.

4. Complete the Dilution: Carefully add ethanol to bring the total volume up to the 100 mL mark on the beaker’s calibration line. Mix thoroughly to ensure homogeneity.

5. Transfer and Store: Transfer the finished solution into a clean glass dropper bottle or reagent bottle. Seal tightly and label with concentration and preparation date. The solution remains stable for several weeks when stored at room temperature, away from direct sunlight.

Applications of EBT Solution

EBT’s azo-dye structure imparts a deep blue (nearly black) color in solution, making it an ideal indicator for:

• Complexometric titrations with ethylenediaminetetraacetic acid (EDTA) to determine water hardness.
• Rapid, visual estimation of pH in aqueous samples: wine‑red indicates pH < 6.3, blue indicates 6.3 – 11.6, and orange indicates pH > 11.6.
• Textile dyeing processes for fur, nylon, silk, and wool, where the dye’s vibrant hues are desirable.

Practical Water Hardness Test Example

1. Place a few milliliters of the water sample in a clean conical flask. 2. Add a few drops of the prepared EBT solution and swirl gently.

• A wine‑red color signals the presence of free Ca²⁺, Mg²⁺, and other metal ions, which bind to EBT and mask the pH readout.

• To assess hardness, prepare a 0.1 % EDTA solution. Gradually add it to the red water while swirling until the color shifts to blue. The volume of EDTA required, combined with its known concentration, yields the total hardness (ppm CaCO₃).

Key Takeaways

• A 0.5 % w/v EBT solution is optimal for both pH and hardness assays.
• Accuracy hinges on precise weighing, thorough dissolution, and careful volumetric adjustment.
• Follow standard laboratory safety protocols to mitigate exposure risks.