Different disulphite salts formed from the mixture of isomeric cyclohexanedione can be explained as follows:

1. Introduction:
In this scenario, we have a mixture containing all isomeric forms of cyclohexanedione. These isomeric forms differ in the position of the carbonyl groups on the cyclohexane ring. When this mixture is treated with an excess of NaHSO3 solution, it undergoes a reaction to form disulphite salts.

2. Reaction:
The reaction between the cyclohexanedione and NaHSO3 proceeds via a nucleophilic addition-elimination mechanism. The nucleophilic sulfur dioxide ion (SO3^2-) attacks one of the carbonyl groups of the cyclohexanedione, leading to the formation of a cyclic intermediate. This intermediate then undergoes elimination of water to form the disulphite salt.

3. Isomerism:
Due to the presence of two carbonyl groups in cyclohexanedione, there are multiple possible isomeric forms. These isomers differ in the position of the carbonyl groups on the cyclohexane ring. The different isomeric forms of cyclohexanedione include:

- 1,2-cyclohexanedione
- 1,3-cyclohexanedione
- 1,4-cyclohexanedione
- 1,2-dimethylcyclohexanedione
- 1,3-dimethylcyclohexanedione
- 1,4-dimethylcyclohexanedione

4. Formation of disulphite salts:
When each of these isomeric forms of cyclohexanedione reacts with NaHSO3, they form different disulphite salts. The disulphite salts are formed by the addition of two SO3^2- ions to the carbonyl groups of the cyclohexanedione, followed by elimination of water. As a result, eight different disulphite salts are formed, corresponding to each isomeric form of cyclohexanedione.

5. Conclusion:
In summary, when a mixture containing all isomeric cyclohexanedione is treated with an excess of NaHSO3 solution, eight different disulphite salts are formed. Each isomeric form of cyclohexanedione reacts differently with NaHSO3, leading to the formation of distinct disulphite salts. This demonstrates the importance of considering isomerism in chemical reactions and the formation of different products based on the structural differences of the reactants.