Coagulation of natural rubber latex: Natural rubber is harvested as an aqueous latex (a colloidal dispersion of polymer particles). Which of the following salts are used as coagulants to destabilize latex and obtain solid rubber?

Introduction / Context:
Latex coagulation converts dispersed rubber particles into a continuous solid. While organic acids (e.g., acetic or formic acid) are widely used, certain multivalent salts (alums) can also neutralize particle charges and trigger coagulation. This tests knowledge of practical coagulants besides acids.

Given Data / Assumptions:

• Latex is a negatively charged colloid stabilized in water.
• We consider inorganic salt coagulants — specifically, ammonium alum and potassium alum.
• Goal: identify which listed salts are effective coagulants.

Concept / Approach:
Coagulation occurs when electrostatic stabilization is disrupted. Trivalent Al3+ from alum salts compresses the electrical double layer and bridges particles. Both ammonium alum and potassium alum supply Al3+ along with sulfate, creating conditions for flocculation and coagulation of latex.

Step-by-Step Solution:
Recognize latex stabilization mechanism: surface charge and double layer.Apply multivalent cation effect: Al3+ promotes rapid coagulation.Conclude that both ammonium alum and potassium alum can coagulate latex.

Verification / Alternative check:
Industrial practice predominantly uses weak acids due to cost and quality control, but alum salts are known coagulants and appear in process literature for special cases or lab use.

Why Other Options Are Wrong:

• Only one alum: unnecessarily restrictive; both work via Al3+.
• Neither: incorrect—alums are effective coagulants.

Common Pitfalls:

• Assuming only acids coagulate latex; salts can, too.
• Confusing stabilization (ammonia preservation) with coagulation; alums counter stabilization.

Final Answer:
both a & b