Some suppliers sell spurious magnesium carbonate made from waste raw materials. Osian describes two simple tests you can run on the material you buy: an acid test for genuineness and a colour test for ammonia and other impurities. For a side-by-side comparison, see the comparative observations.
Test 1: Is the magnesium carbonate genuine? (acid test)
- Take 2 g of the magnesium carbonate.
- Add 10 ml of dilute sulfuric acid (10 ml of 98% sulfuric acid made up with 90 ml of water). Carbon dioxide bubbles are released.
- Genuine material gives a clean, clear solution with no black or brown colouration and no undissolved particles.
- Undissolved particles suggest mixing with cheap material. A blackish or brownish dense colour indicates impurities and ammonia.
Safety: sulfuric acid is corrosive. Always add the acid slowly to the water, never the reverse, wear gloves and eye protection, and work in a ventilated place.
Test 2: Colour test for ammonia and hazardous impurities
The test packet contains 2 bottles, A and B. Half-fill each bottle with mineral water, dissolve the chemical well, top up with water and stir, then let it stand. This is reagent A. Prepare reagent B the same way.
Method
- In an empty glass, take one teaspoon of the magnesium carbonate and half a glass of water, and stir well.
- Add about 2 teaspoons of reagent A and stir.
- Then add about 2 teaspoons of reagent B.
| Colour stays white | Original magnesium carbonate (made from soda ash) |
| White to pale yellow | Mixed material: original plus duplicate (NH4-MgCO3) |
| White to dark yellow or brown | 100% duplicate magnesium carbonate; ammonia and other impurities present |
Note: the reagents are hot while they are being prepared, so let them stand for an hour before use.
Related
Comparative observations · How magnesium carbonate is made · Quality policy · Light Magnesium Carbonate
