How many of the following are negatively charged sols ?
Silver sol, `Cr(OH)_(3)` sol, `As_(2)S_(3)` sol, starch sol, silicic acid sol, haemoglobin, congo red dye, prussion blue, gum, clay, charcoal.

Explanation

To determine how many of the given sols are negatively charged, we will analyze each sol individually and identify their charge characteristics.

### Step-by-Step Solution:

1. **Identify the sols**: The sols given are:
- Silver sol
- `Cr(OH)_(3)` sol
- `As_(2)S_(3)` sol
...