Question

Out of the following, the most appropriate dyestuff for the coloration of silk is:

• A. Vat dyes
• B. Acid dyes
• C. Sulphur dyes
• D. Disperse dyes

Hint:

Always consider the nature of the fiber when selecting the type of dyestuff to ensure optimal results.

Answer 1

The Correct Option is B

Step 1: Concept
Silk is a protein fiber, and the choice of dye depends on the nature of the fiber and its surface characteristics. Different types of dyestuffs have specific solubility and affinity for various fibers.

Step 2: Meaning
Vat dyes are highly light and wash fast, but they require reduction before use. Acid dyes are used for synthetic and protein fibers with acidic mordants. Sulphur dyes are used for cellulosic fibers. Disperse dyes are used for synthetic fibers in the dispersion process.

Step 3: Analysis
Silk is a protein fiber, primarily composed of fibroin, which has a high affinity for certain types of dyes. Acid dyes are known to have good affinity for silk due to their acidic nature and ability to form complexes with the amino groups present on the surface of silk proteins. This makes acid dyes suitable for dyeing silk without requiring harsh conditions or additional chemicals. Vat dyes, while highly colorfast, require a reduction process which is not ideal for silk as it can damage the fiber structure. Sulphur dyes are typically used for cellulosic fibers and do not have the same affinity for protein fibers like silk. Disperse dyes are designed for synthetic fibers in the dispersion process and are not suitable for protein fibers.

Step 4: Conclusion
Given that acid dyes have a good affinity for silk and can be applied directly without requiring harsh conditions or additional chemicals, they are the most appropriate choice for dyeing silk. Final Answer: (B)