Question

A cotton fabric is treated with a finishing chemical of 6.0 % concentration. If the wet pick up is 80 %, the add-on of chemical on fabric is \(\underline{\hspace{2cm}}\)

• A. 1.48 %
• B. 4.8 %
• C. 3.48 %
• D. 0.48 %

Hint:

The formula is: Add-on % = Wet Pick Up % \( \times \) Concentration %. Think of it logically: The fabric picks up a certain amount of liquid (Wet Pick Up), and that liquid contains a certain amount of chemical (Concentration). The product of the two gives the amount of dry chemical on the fabric.

Answer 1

The Correct Option is B

Step 1: Understand the terms.
- Concentration: The percentage of chemical in the finishing solution. Here, 6.0%. This means 6g of chemical per 100g of solution.
- Wet Pick Up (WPU): The percentage of solution that the fabric picks up relative to its own dry weight. Here, 80%. This means a 100g dry fabric will pick up 80g of solution.
- Add-on: The percentage of dry chemical that is added to the fabric relative to its own dry weight.

Step 2: Use the formula for calculating add-on.
Add-on (%) = Wet Pick Up (%) \( \times \) Concentration (%) / 100
or
Add-on (%) = WPU \( \times \) Concentration

Step 3: Substitute the given values.
Add-on (%) = \( 80% \times 6.0% \)
Add-on (%) = \( 0.80 \times 0.06 = 0.048 \)
To express this as a percentage, multiply by 100: \( 0.048 \times 100 = 4.8% \). Alternatively, using the first formula: Add-on (%) = \( \frac{80 \times 6.0}{100} = \frac{480}{100} = 4.8% \). This means that for every 100g of dry fabric, 4.8g of dry chemical is added.