Preservatives, developing agents

During the development process the developing agent is oxidized, rendering it useless. However, developers will oxidize even without the development process. To prevent this, or at least inhibit the rate of oxidation, a preservative is added to the developer. 

Technique of Divided Development In divided development, two separate baths are used. The first bath contains the developing agent(s), restrainer, and preservative. The second bath contains the accelerator. The second bath is used to activate the developer. Borax is the least active accelerator metaborate is about double the strength of borax carbonate is about double the strength of metaborate. Hydroxide is the most active of the alkalis and the least controllable. 

As a developing agent, catechol tans the surface gelatin of the negative (see Tanning Developers, below). It is also easy to use catechol to compound formulas that create a desirable image stain density when low quantities of preservative (e.g., sodium sulfite) are used (see Image Stain, below). Both of these properties it shares in common with pyro. 

Unless otherwise specified, always dissolve the ingredients in the order given. In developers, the sulfite is usually dissolved first because most developing agents are easily oxidized in water without this preservative. 

Uses As a preservative of developing agents constituent of the acid fixing bath blackener in negative intensification active energizer in amidol development. 

NOTE 1 To help preserve the developing agents in Solution A, measure out the sodium bisulfite first and add a pinch to the water before the metol. Set the remainder of the bisulfite aside and add it in proper sequence. 

Hydroquinone and A -methyl-/j-aminophenol (Metol) form a superadditive mixture which was shown by Tausch and Levenson [47] to involve the consumption primarily of hydroquinone with the preservation of Metol. This led to the regeneration theory proposed by Levenson, that Metol was acting as the developing agent at the silver halide surface and that oxidized Metol was reduced back to Metol by hydroquinone as outlined in Eqs. (30)-(33). 

Use Paper industry (semichemical pulp), reducing agent (dyes), water treatment, photographic developer, food preservative and antioxidant, textile bleaching (antichlor). 

If a pharmaceutical company manufactures a multidose formulation, the timeline for the development of this dose is significantly greater than for a unit dose formulation. A multidose will require the incorporation of an antimicrobial agent (preservative) in the protein formulation. 

Uses Preservative for photographic developers antioxidant, buffer in cosmetics nutrient, dietary supplement, color fixing agent, flavoring agent, preservative, antioxidant, oxidant in foods pharmaceutical antioxidant animal feed Regulatory FDA 21CFR 101.9, 101,14, 107.100, 137.105, 137.155, 137.160, 137.165, 137.170,... 

Clear organic coatings have been developed to preserve the attractive, bright, as-polished, zinc, zinc alloy, or zinc-coated surfaces. The coatings may be either acrylic or polyurethane lacquers or polyester powders and may be colorless or tinted, usually to simulate brass. They usually incorporate ultraviolet absorbers and a complexing agent for zinc (dithiooxamide). They have only a limited life and, in the atmosphere, usually must be renewed after 3-10 years (depending on the environment) to retain appearance. 

Photography. Sodium sulfite is useful as a reducing agent in certain photographic fixing baths, developers, hardeners, and intensifiers (334). However, the principal use is as a film preservative and discoloration preventative (see Photography). 

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