Final answer:
Silica gel can be used as a diluent in tablet formulations to enhance firmness without reacting with sugars, acting as a filler and desiccant. Other potential additives for increasing tablet firmness are synthetic polymers such as certain types of polyethylene glycol.
Step-by-step explanation:
Diluents are commonly used in the production of tablets to increase volume and improve physical properties like firmness. An example of a diluent that can be added to tablets to enhance firmness without a chemical reaction with sugars is silica gel. This substance acts both as a filler and as a desiccant, contributing to the structural integrity of the tablet.
Carboxymethyl cellulose is an example of an anti-redeposition agent but is also known for its tablet disintegration properties, making it a less likely choice as a firmness enhancer. For tablets that specifically require non-sugar-based firmness, synthetic polymers, like certain types of polyethylene glycol (PEG), are also a viable option. These ingredients help in maintaining the tablet's cohesive properties, ensuring that they do not crumble during handling or storage.