INBDE (Integrated National Board Dental Examination) Practice Exam

In photographic film processing, hydroquinone, phenidone, selenium, and gelatin are all used as reducing agents to help develop the silver ions to metallic silver. However, they are not all used at the first stage of the process. Hydroquinone and phenidone are used as the primary developing agents, while selenium is used as a toning agent and gelatin is used as a binder for the light-sensitive silver halide crystals. Therefore, the most appropriate answer for the first electron donor that reduces silver ions to metallic silver at the latent image site is phenidone.