Out of the following, the compound which is not a coordination compound is :

Options

A. `[Co(NH_3)_4Cl_2]^(+)`
B. `[FeSO_4(NH_4)_2SO_4. 6H_2O`
C. `K_3Fe(CN)_6`
D. `K_4Fe(CN)_6`

Explanation

To determine which compound is not a coordination compound, we need to analyze the given options based on the properties of coordination compounds and double salts.

### Step-by-Step Solution:

1. **Understanding Coordination Compounds**:
Coordination compounds are characterized by the presence of a central metal atom or ion bonded to surrounding ligands. When these compounds dissolve in water, they typically dissociate into their constituent ions, losing their original identity.

2. **Understanding Double Salts**:
Double salts, on the other hand, are compounds that consist of two different salts that crystallize together. When dissolved in water, they do not dissociate into their individual ions but retain their identity as a whole compound.

3. **Analyzing the Options**:
- **Option A**: This is a coordination compound as it loses its identity in solution.
- **Option B**: This is a double salt (ferrous ammonium sulfate) which retains its identity in solution, producing ferrous ions, sulfate ions, and ammonium ions without dissociating completely.
- **Option C**: This is a coordination compound as it loses its identity in solution.
- **Option D**: This is also a coordination compound as it loses its identity in solution.

4. **Conclusion**:
Among the options, **Option B (ferrous ammonium sulfate)** is the compound that is not a coordination compound because it retains its identity in solution and does not dissociate into individual ions.

### Final Answer:
The compound which is not a coordination compound is **Option B (ferrous ammonium sulfate)**.