Recent X-ray work, IR and other spectroscopic methods have proved that Turnbull's blue is identical to Prussian blue.
Q. What is the common formula of Turnbull's blue and Prussian blue?

Options

A. `Fe_(3)[Fe(CN)_(6)]_(2)`
B. `Fe_(4)[Fe(CN)_(6)]_(3)`
C. `KF e[Fe(CN)_(6)]`
D. `KF e_(2)[Fe(CN)_(6)]`

Answer

To determine the common formula of Turnbull's blue and Prussian blue, we can follow these steps:

### Step 1: Identify the compounds
Turnbull's blue and Prussian blue are both known as dark blue pigments. They are used in various applications, including paints and blueprints.

### Step 2: Understand the chemical composition
Prussian blue is also known as ferric ferrocyanide, and its chemical formula is often represented as \( \text{Fe}_3[\text{Fe(CN)}_6]_2 \). Turnbull's blue is similar in structure and is known as ferrous ferrocyanide, with the formula \( \text{Fe}_3[\text{Fe(CN)}_6]_2 \) as well.

### Step 3: Write the common formula
Both Turnbull's blue and Prussian blue can be represented by the formula \( \text{Fe}_3[\text{Fe(CN)}_6]_2 \) or \( \text{Fe}_4[\text{Fe(CN)}_6]_3 \) when considering the overall stoichiometry. However, the most commonly accepted formula for both is \( \text{Fe}_3[\text{Fe(CN)}_6]_2 \).

### Conclusion
The common formula of Turnbull's blue and Prussian blue is \( \text{Fe}_3[\text{Fe(CN)}_6]_2 \).

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