Developing agents accelerators

Increasing the amount of accelerator in a developer will increase the contrast. This is because it creates a more active environment in which the developing agent can reduce additional silver halide in the exposed areas. However, too much accelerator will increase fog levels, necessitating the addition of bromide or some other form of restrainer. While paper developers should always contain some restrainer, when formulating a film developer it is better to decrease the accelerator rather than add more restrainer. 

Also, the higher the pH, the faster a developer will oxidize. To prevent oxidation, developers often are stored in separate A and B solutions that are mixed just prior to use. Developers using caustic alkali should always be formulated in this manner. Developers containing easily oxidized developing agents, such as pyro, should also be stored this way, regardless of which accelerator is used. 

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. 

Uses High-energy accelerator or alkali sometimes used to activate low-energy developing agents (e.g., hydroquinone). 

The beneficial action of triamcinolone appears to be related to its inhibition of synthesis of inflammatory mediators (prostaglandins and interleukins), inhibition of the VEGF gene, and improved stability of the blood-retinal barrier. The rise in intraocular pressure typically occurs in 40% to 50% of patients but is controllable with one or two topical antiglaucoma agents. Other complications of IVTA include ptosis, endophthalmitis, accelerated development of cataract, and retinal detachment. The most worrisome compUcation is infectious endophthalmitis, but the incidence of cases is quite low. 

Another complicating factor is that the oxidized form of the developing agent can in some cases accelerate rather then retard development, as in the case of Lith development. 

It is proposed that the semiquinone is an active developing agent, estimated by Umberger [64] to be 10 times as active as the hydroquinone dianion. The low sulfite level in Lith developers allows the p-benzoquinone (Q) to build up, which boosts the semiquinone concentration via the dismutation reaction. The increased semiquinone level accelerates development which produces more p-benzoquinone and semiquinone according to Eqs. (46), (47),... 

Use Azo dye intermediate, photographic developing agent, photochemical measurements, intermediate in manufacture of antioxidants and accelerators for rubber, synthetic fibers, laboratory reagent, dyeing hair and fur. 

MAJOR USES Used in the production of dyes photographic developing agent vulcanization accelerator antioxidant in rubber compounds accelerator for synthetic fibers laboratory reagent photochemical measurements. 

The oxidation of the compounds used as developers is accelerated in the presence of alkalies and retarded by acids for this reason most developers are made up just before use from two solutions, one containing the developing agent, and the other sodium carbonate. 

Uses Azo dye intermediate photographic developing agent intermediate in mfg. of antioxidants, accelerators for rubber, synthetic fibers colorant for hair dyes, fur laboratory reagent... 

Follow-up after modernization. Contact Dermatitis 20 191-200 Liden C (1990) Persulfate bleach accelerator - a potent contact allergen in film laboratories chemical identification, purity studies, and patch testing. Am J Contact Dermatitis 1 21-24 Liden C, Boman A (1988) Contact allergy to colour developing agents in the guinea pig. Contact Dermatitis 19 290-295... 

Three different covalent cure systems are commonly used sulfur-based or sulfur donor, peroxide, and maleimide. These systems rely on a cross-linking agent and one or more accelerators to develop high cross-link density. 

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