Surface tension of a liquid is a molecular phenomenon of liquids involving the force of cohesion along the liquid molecules. It is scalar quantity and is numberically equal to the surface energy. Numerically, it is proved that the potential soluble salts and surface active substance. Sparingly soluble salts and surface active substances decrease the surface tension of the liquid. However, the fairly soluble solutes increase the surface tension of the liquid. Surface tension of a liquid is independent of surface area but it depends on the intermolecular forces and the temperature.
Which among the following is not the unit of surface tension ?

Options

A. `"dyne"//"cm"`
B. `"newton"//m`
C. `J//m^(2)`
D. `erg//cm`.

Explanation

To determine which among the given options is not a unit of surface tension, we first need to understand the definition and units associated with surface tension.

### Step-by-Step Solution:

1. **Understanding Surface Tension**:
Surface tension is defined as the force acting along the surface of a liquid per unit length. It arises due to cohesive forces between liquid molecules.

2. **Formula for Surface Tension**:
The formula for surface tension (γ) can be expressed as:
\[ \gamma = \frac{F}{L} \]
where \( F \) is the force acting along the surface, and \( L \) is the length over which the force acts.

3. **Units of Surface Tension**:
- The SI unit of force is Newton (N), and the unit of length is meter (m). Therefore, the SI unit of surface tension is:
\[ \text{Surface Tension} = \frac{\text{N}}{\text{m}} \quad \text{(Newton per meter)} \]
- In the CGS system, force can be measured in dyne and length in centimeter (cm), leading to another unit:
\[ \text{Surface Tension} = \frac{\text{dyne}}{\text{cm}} \quad \text{(dyne per centimeter)} \]

4. **Exploring Other Units**:
- Joule (J) is a unit of energy, defined as \( \text{N} \cdot \text{m} \). If we were to express surface tension in terms of energy, we could manipulate the formula, but it would not yield a valid unit for surface tension directly.
- If we consider Joules per meter squared (\( \text{J/m}^2 \)), it could be related to surface energy, but it is not a direct unit of surface tension.

5. **Identifying the Incorrect Unit**:
- If we analyze the options provided, we can conclude that **arg per centimeter** (arg/cm) is not a valid unit of surface tension. Arg is a unit of energy, and it does not relate to the definition of surface tension.

### Conclusion:
The unit that is **not a unit of surface tension** is **arg per centimeter**.