Which of the following statements are CORRECT about soap?

(I) Transparent soaps are made by dissolving the soap in ethanol and then evaporating the excess solvent.

(II) Shaving soaps contain sodium rosinate to prevent rapid drying.

(III) Dye does not absorb evenly on cloth washed with soap using hard water, because of insoluble gummy precipitate.

The correct answer is Option 2.

Key Points

• Transparent soaps are indeed made by dissolving soap in ethanol and then evaporating the excess solvent to achieve clarity.
• In shaving soaps, sodium rosinate is used to prevent rapid drying and to produce a long-lasting lather.
• When washing with soap in hard water, the presence of calcium and magnesium ions leads to the formation of an insoluble gummy precipitate, which hinders even absorption of dye on cloth.

Additional Information

• Hard Water:
  • Water with high mineral content, primarily calcium and magnesium ions, is termed hard water.
  • It reduces the effectiveness of soap by forming scum or precipitate.
• Ethanol in Soap Making:
  • Ethanol is used to dissolve soap and create transparent soaps.
  • It helps in the saponification process and achieves clarity in the final soap product.
• Sodium Rosinate:
  • A sodium salt of rosin acid used in shaving soaps.
  • It provides stability and enhances the texture of the soap lather.
• Soap Scum:
  • Soap scum is an insoluble residue formed when soap is used in hard water.
  • This residue can affect the texture and appearance of fabrics.