Qualitative analysis of organic compounds is performed by Lassaigne's test by fusion with metallic sodium, by which the covalent compounds are converted into ionic compounds. Extra elementsline `N,S,P` andhalogensaredetected by their usual tests.
Q. Blood-red colour in the detection of both `N` and `S` in lassaigne's extract is due to the formation of :

Options

A. `Fe(CNS)_2`
B. `Fe(CNS)_3`
C. `K_4[Fe(CN)_6]`
D. `K_3[Fe(CN)_6]`

Answer

To solve the question regarding the blood-red color observed in the detection of both nitrogen (N) and sulfur (S) in Lassaigne's extract, we can follow these steps:

### Step 1: Understand Lassaigne's Test
Lassaigne's test is a qualitative analysis method used to detect the presence of certain elements in organic compounds. When organic compounds are fused with metallic sodium, they are converted into ionic compounds, allowing for the detection of elements like nitrogen, sulfur, phosphorus, and halogens.

**Hint:** Remember that Lassaigne's test involves the fusion of organic compounds with sodium to form sodium salts.

### Step 2: Identify the Reaction
In the presence of sulfur and nitrogen, sodium reacts with carbon and sulfur to form sodium thiocyanate (NaSCN). The thiocyanate ion (SCN⁻) is crucial for the subsequent detection of nitrogen and sulfur.

**Hint:** Look for the formation of thiocyanate ions during the reaction with sodium.

### Step 3: Reaction with Ferric Ion
The thiocyanate ion (SCN⁻) then reacts with ferric ions (Fe³⁺) to form ferric thiocyanate (Fe(SCN)₃). This compound is responsible for the characteristic blood-red color observed in the test.

**Hint:** Focus on the interaction between thiocyanate ions and ferric ions to produce a colored complex.

### Step 4: Conclusion
The blood-red color in the detection of both nitrogen and sulfur in Lassaigne's extract is due to the formation of ferric thiocyanate (Fe(SCN)₃).

**Final Answer:** The blood-red color is due to the formation of ferric thiocyanate (Fe(SCN)₃).

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