The incorrect statements are -

Options

A. For coagulation of `As_(2)S_(3)` sol, +ve ions are effective.
B. For coagulation of aluminium hydroxide sol `Ba^(2+)` ions are more effective than `Na^(+)`
C. Cellulose solution is an example of multimolecular colloid system
D. Colloidal sol of metals such as gold, silver etc are prepared by Bredig's arc method.

Explanation

To determine the incorrect statements from the provided options, we will analyze each statement one by one.

### Step 1: Analyze Statement A
**Statement A:** For coagulation of AS2-S3 salt, positive ions are effective.

- **Analysis:** AS2-S3 (arsenious sulfide) is a negatively charged colloidal particle. Coagulation of negatively charged colloids is achieved by adding positive ions, which neutralize the charge and allow the particles to aggregate.
- **Conclusion:** This statement is **correct**.

### Step 2: Analyze Statement B
**Statement B:** For coagulation of aluminium hydroxide, barium 2+ ions are more effective than Na+.

- **Analysis:** Aluminium hydroxide is a positively charged colloid. For coagulation of positively charged colloids, negative ions are more effective. Since barium 2+ is a positive ion, it is not effective for coagulating aluminium hydroxide. Sodium ions (Na+) are also positive and thus, this statement is incorrect.
- **Conclusion:** This statement is **incorrect**.

### Step 3: Analyze Statement C
**Statement C:** Cellulose solution is an example of a multi-molecular colloid system.

- **Analysis:** Cellulose is a macromolecule and forms a macromolecular colloid, not a multi-molecular colloid. Multi-molecular colloids consist of small particles, while macromolecular colloids consist of large molecules.
- **Conclusion:** This statement is **incorrect**.

### Step 4: Analyze Statement D
**Statement D:** Colloidal salt of Bredick's arc method.

- **Analysis:** The Bredick's arc method is indeed an electrical disintegration method used to prepare colloidal solutions of metals such as gold, platinum, and silver. This statement is accurate.
- **Conclusion:** This statement is **correct**.

### Final Conclusion
The incorrect statements are **B and C**.