In the calgon process of softening of water, which of the following is used ?

Options

A. Sodium polymetaphosphate
B. Hydrated sodium aluminium silicate
C. Cation exchange resins
D. Anion exchange resins

Answer

To solve the question regarding the Calgon process of softening water, we need to identify the correct agent used in this process. The options provided are:

1. Sodium polymetaphosphate
2. Hydrated sodium aluminum silicate
3. Cation exchange resin
4. Anion exchange resin

### Step-by-Step Solution:

**Step 1: Understand the Calgon Process**
The Calgon process is a method used to soften hard water, specifically aimed at removing permanent hardness caused by calcium and magnesium ions.

**Step 2: Identify the Chemical Agent Used**
The key chemical agent used in the Calgon process is sodium hexametaphosphate, which is also known as sodium polymetaphosphate. This compound helps to sequester calcium and magnesium ions, preventing them from forming insoluble precipitates.

**Step 3: Analyze the Options**
- **Sodium polymetaphosphate**: This is the correct answer as it is synonymous with sodium hexametaphosphate, used in the Calgon process.
- **Hydrated sodium aluminum silicate**: This is not the primary agent used in the Calgon process.
- **Cation exchange resin**: While cation exchange resins can soften water, they are not specifically part of the Calgon process.
- **Anion exchange resin**: This is also not relevant to the Calgon process.

**Step 4: Conclusion**
Based on the analysis, the correct answer is **sodium polymetaphosphate**.

### Final Answer:
The agent used in the Calgon process of softening water is **sodium polymetaphosphate**.

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