What is the role of sodium sulphite in preventing oxidation in developers?

Sodium sulphite's role in photographic developers is to prevent oxidation, making it a crucial component in the photographic processing of film or paper. It acts as a preservative, which allows the developer solution to remain effective for a more extended period by protecting it from the oxidation that would degrade its chemicals and efficacy. This preservation is vital as developers can be sensitive to exposure to air and light, and sodium sulphite helps to mitigate these effects, ensuring consistent performance across multiple uses.

Understanding the specific function of sodium sulphite is essential because it highlights the chemical interactions that are necessary for achieving optimal results in image production. Other options, while relevant to some aspects of developer chemistry, do not accurately reflect the primary function of sodium sulphite. For instance, while it does help in maintaining chemical stability, it does not act as a buffer or a restrainer. It also does not increase acidity, which is a separate concern altogether in the development process. Thus, recognizing sodium sulphite as a preservative directly relates to its role in enhancing the longevity and reliability of developers in photography.