Why is sodium carbonate extract acidified before perfoming the confirmatory tests for anions?

Explanation

### Step-by-Step Solution:

1. **Understanding the Role of Sodium Carbonate**: Sodium carbonate (Na2CO3) is commonly used in qualitative analysis as it can extract anions from a mixture. However, it also contains carbonate ions itself.

2. **Heating with Test Reagents**: When sodium carbonate extract is heated with certain test reagents, the carbonate ions can react and precipitate certain metal carbonates. This can lead to confusion in the analysis as these precipitates may mask or interfere with the detection of the desired anions.

3. **Interference in Detection**: The presence of carbonate ions can lead to the formation of insoluble carbonates when mixed with metal ions. This can result in false positives or negatives in the confirmatory tests for anions.

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