Multiple choice

Which of the following dyes are generally used as pH indicators and as biological stains?

  1. Acid dyes

  2. Basic dyes

  3. Direct dyes

  4. Vat dyes
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Direct or substantive dyeing is normally carried out in a neutral or slightly alkaline dyebath, at or near boiling point, with the addition of either sodium chloride (NaCl) or sodium sulfate (Na2SO4). Direct dyes are used on cotton, paper, leather, wool, silk and nylon. They are also used as pH indicators and as biological stains.

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