Question

Diazo reagent is :

1. Sulphanilic acid in Hydrochloric acid
2. Sodium nitrite solution
3. Sulphanilic acid in water
4. Sulphanilic acid in Sulphuric acid

• A. (i) only
• B. (i) and (ii)
• C. (ii) and (iii)
• D. (ii) and (iv)

Answer 1

Answer:

B. (i) and (ii)

Understanding the Diazo Reagent

• The Diazo reagent, frequently utilized in clinical and food chemistry testing (such as the detection of bilirubin or specific food additives like nitrites), is essentially a solution of Sodium nitrite (NaNO₂).
• In standard laboratory protocols, particularly the Ehrlich's Diazo reaction, the reagent is prepared in two parts:
  • Reagent A: Sulphanilic acid dissolved in Hydrochloric acid (HCl).
  • Reagent B: Sodium nitrite (NaNO₂) solution.
• The actual diazotization process occurs when these two reagents are mixed. The Sodium nitrite reacts with the acid to form nitrous acid (HNO₂), which then reacts with the aromatic amine (sulphanilic acid) to form the diazonium salt.
• Therefore, while Sulphanilic acid is a critical component for the reaction to proceed, the specific chemical component often referred to as the 'Diazo reagent' or 'Diazo solution' in testing kits is the Sodium nitrite solution, which initiates the formation of the active diazonium cation.
• Key Application: This reaction is widely used in Food Technology for the determination of nitrites in meat products and in medical diagnostics for checking bilirubin levels in serum or urine.