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4 Chemical solubility tests (Fig 4)

Fig 4

This method involves testing the solubility of fibers in 3 Observe whether the fiber dissolves, swells, or
specific chemical reagents. Different fibers dissolve remains unchanged. Gentle heating might be required
or react differently with various acids, alkalis, and for some tests.
organic solvents. This is generally more definitive for 5 Staining tests (Dye tests)
differentiating between synthetic fibers that might look
similar under a microscope. These tests utilize specific dyes or mixtures of dyes that
react differently with various fiber types, producing distinct
• Common reagents and reactions
colors. They are particularly useful for identifying fibers
- Acetone: Dissolves Acetate and Triacetate. in blends or confirming other tests.
- Formic Acid (Concentrated): Dissolves Nylon. 1 Clean the fiber sample (remove any finishes or dyes).
- Sulfuric Acid (conc.): Dissolves Cotton, Rayon, 2 Immerse the fiber in a specially formulated stain
Linen, Silk, Wool, Nylon. Does NOT dissolve solution for a specific time and temperature.
Polyester, Acrylic, Polypropylene. (Useful for 3 Rinse the fiber and observe the color.
identifying blends where one component dissolves
and the other doesn’t). • Examples of stains
- Sodium hypochlorite (Bleach): Dissolves Silk - Shirlastain A or B: Common laboratory stains
and Wool (protein fibers). Does NOT dissolve that produce a range of colors for different
cellulosic or synthetic fibers. fibers.
- Phenol: Dissolves Polyester. - Cotton/viscose: Purple/Blue

- Boiling Dimethy Formamide (DMF): Dissolves - Wool/silk: Yellow/Brown
Acrylic. - Nylon: Pink/Red
- Hydrochloric acid (conc.): Dissolves Nylon. - Polyester: Pale yellow/undyed
- Cuprammonium hydroxide (Cuene): Dissolves • Iodine-potassium iodide solution: Stains
Cotton, Rayon (but not Linen as readily). cellulosic fibers blue/purple.
1 Place a small fiber sample in a test tube or watch • Picric acid: Stains protein fibers yellow.
glass.
2 Add a few drops of the specific chemical reagent.

6 Textile & Handloom: Shawl Weaving Artisan : (NSQF - 2024) R.T. Ex.No 1.1.02&07