Multiple choice

Which of the following materials is/are used to prepare blue-black ink?

  1. Gallic acid

  2. Tannic acid

  3. Ferrous sulphate

  4. All of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Traditional blue-black ink (iron gall ink) is prepared using ferrous sulphate along with gallic acid and tannic acid. These components react to form the dark-colored pigment. All three ingredients are essential for proper ink formulation.

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