🌟 LIMIT TEST OF BORON – Full Practical | Pharmaceutical Inorganic Chemistry (Semester-1)

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Welcome back to PharmaEasyNotes!

We’ve already covered major limit tests like Chloride, Sulphate, Iron, Heavy Metals, Lead, Arsenic, and Nitrate.

Now let’s study another important and rarely explained practical:

 LIMIT TEST FOR BORON

This test is used to detect traces of borates in pharmaceutical substances.

⭐ 1. Aim

To detect the presence of boron (as borates) in a pharmaceutical substance using curcumin reagent.

⭐ 2. Principle

Boron reacts with Curcumin (a natural yellow pigment) in an acidic medium to form a red-colored compound called Rosocyanine.

📌 If boron is present → Red/Pink color appears

No boron → Solution remains yellow.

⭐ 3. Chemicals Required

• Curcumin Reagent

• Sulphuric Acid (Concentrated)

• Ethanol

• Sample solution

• Standard Boron solution (for comparison)

⭐ 4. Apparatus Required

• Test tubes

• Pipettes

• Water bath

• Measuring cylinder

• Beaker

⭐ 5. Procedure

Step 1 — Sample Preparation

Take 2 mL of the test solution in a test tube.

Step 2 — Add Curcumin Reagent

Add 2 drops of curcumin reagent.

Step 3 — Add Acid

Add 1 mL of concentrated sulphuric acid slowly.

Step 4 — Heat

Heat the mixture on a water bath for 10 minutes.

Step 5 — Compare

Prepare a standard boron solution using the same steps.

👉 Compare the color intensity of the test with standard.

⭐ 6. Observation Table

S. No.	Sample	Color Change	Result
1	Test Solution	___	___
2	Standard Solution	Pink/Red	Positive Control

⭐ 7. Result

The amount of boron in the given sample is within / beyond the specified limit (write as per observation).

⭐ 8. Viva Questions (High Scoring!)

❓ 1. What reagent is used in limit test of boron?

➡ Curcumin reagent.

❓ 2. What is the principle?

➡ Formation of red-colored rosocyanine with boron.

❓ 3. Why is sulphuric acid added?

➡ To provide acidic medium for reaction.

❓ 4. What color confirms presence of boron?

➡ Pink to red color.

❓ 5. Which drugs may contain boron contaminants?

➡ Boric acid preparations, buffer solutions, eye-wash formulations.

💬 Ask Your Students:

👉 “Which limit test do you want next—Fluoride, Insoluble Ash, or Organic Impurities?”

(Place this in a comment box 

📌 Poll Options:

• Limit Test for Fluoride

• Limit Test for Insoluble Ash

• Limit Test for Organic Impurities

• Limit Test for Sulphated Ash