This is 1 lb of anhydrous Sodium Sulfite from Photographers' Formulary. It is most commonly used as a preservative in developing agents and is also an active energizer in Amidol development. It is also used within acid fixing baths and as a blackener for negative intensification processes.
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Sulfite of Soda Sodium sulfite anhydrous Disodium sulfite Sulfurous acid, disodium salt Exsiccated sodium sulfite
White granular crystals or powder
As a preservative of developing agents Constituent of the acid fixing bath Blackener in negative intensification Active energizer in Amidol development To clear Polaroid Type 55 black & white negatives
Sodium sulfite is the most widely used preservative in developers. It also plays an important part in the process itself.