Dimezone S

Developing AgentC11H14N2OCAS: 13047-13-7Shelf life: 48 mo

Physical Properties

  • Molecular Weight: 206.24 g/mol
  • Solubility (20°C): 100 g/L

Also known as: 4,4-Dimethyl-1-phenyl-3-pyrazolidone, 4-Methylphenidone, DMPS

Dimezone-S (4-hydroxymethyl-4-methyl-1-phenyl-3-pyrazolidone; C₁₁H₁₄N₂O₂; CAS 13047-13-7) is an enhanced phenidone derivative — a pyrazolidone developing agent with higher activity per gram than phenidone and meaningfully better solution shelf life.[1] Marketed under the Dimezone-S trade name (Agfa's specialty grade, now distributed under various manufacturer names since the Agfa dissolution), it has become the preferred phenidone-family agent in premium DIY developer formulations and in contemporary commercial fine-grain developers that demand long working life from a concentrate.

Photographic uses

  • Substitute for phenidone in any PQ formula: Use at roughly 80% of the phenidone concentration for equivalent activity. Microphen, ID-62, and related PQ developers work identically with dimezone-s substituted for phenidone.
  • Hydroquinone-free premium developers: Ascorbate-based formulas (PC-TEA, many Gainer formulas) often use dimezone-s specifically for its stability in the organic-solvent concentrate.
  • Replenished commercial developer systems: Dimezone-s's resistance to oxidation makes it valuable in high-volume replenisher workflows.

Practical notes

Supplied as fine white crystalline powder. More expensive than plain phenidone — typically 2–3× the per-gram cost from specialty suppliers. Sparingly soluble in cold water; dissolve in a small volume of propylene glycol or warm water before adding to the main formula, exactly as with phenidone.

Solution stability: a dimezone-s working developer keeps noticeably longer than its phenidone equivalent — typically 2× the tray life. This is the feature that justifies the cost premium for DIY workers running single-session high-volume work.

Related compounds

Phenidone is the parent compound — Dimezone-S differs by the 4,4-disubstituted methyl/hydroxymethyl groups that stabilize the molecule against oxidation. Dimezone (without the -S suffix) is a different closely-related compound sometimes confused with dimezone-s; verify which one a formula specifies.

Safety Notes

Acute hazards

Dimezone-S has low acute toxicity — essentially the same profile as phenidone:

  • Mild skin and eye irritant in concentrated solution.
  • Not a documented skin sensitizer at normal darkroom exposure.
  • Low inhalation risk; fine powder is mildly irritating.

Storage & handling

  • Personal protective equipment: Nitrile gloves and safety glasses for concentrated-solution work; optional for working-strength developer.
  • Storage: Tightly sealed in a cool dry cabinet.

First aid

Consult the full Sigma-Aldrich Safety Data Sheet for authoritative first-aid instructions.[2]

  • Skin contact: Rinse with water.
  • Eye contact: Flush with running water for at least 10 minutes.
  • Ingestion: Rinse mouth; seek medical attention for substantial swallow.

References

  1. BOOK Anchell, Steve; Troop, Bill. The Film Developing Cookbook 2nd ed. Routledge, 2019. ISBN 9781138959187. ↩
  2. WEB Sigma-Aldrich (Merck KGaA). Sigma-Aldrich Safety Data Sheets Sigma-Aldrich. https://www.sigmaaldrich.com/US/en/search/safety-data-sheets ↩

Reference databases

Last reviewed 2026-04-22