Divided developers formulas

This is one of the best divided developer formulas for fine grain and full tonal scale. For the first bath you can use classic D-23 or a modified version, given here. This is because when... 

This formula can also be used as a divided developer. To use as a two-solution developer try 4 minutes at 68F/20C followed by 3 minutes in a 2% borax solution. Use intermittent agitation in the first solution and gentle but continuous agitation in the second solution. This will prevent uneven development, especially with 120 roll film. For higher contrast lighting, increase exposure and shorten the time in the first solution. 

Catalyst Effectiveness. Even at steady-state, isothermal conditions, consideration must be given to the possible loss in catalyst activity resulting from gradients. The loss is usually calculated based on the effectiveness factor, which is the diffusion-limited reaction rate within catalyst pores divided by the reaction rate at catalyst surface conditions (50). The effectiveness factor E, in turn, is related to the Thiele modulus,

first-order rate constant, a the internal surface area, and the effective diffusivity. It is desirable for E to be as close as possible to its maximum value of unity. Various formulas have been developed for E, which are particularly usehil for analyzing reactors that are potentially subject to thermal instabilities, such as hot spots and temperature mnaways (1,48,51). 

As we recall from the previous chapter [5], the nonlinearity measure we devised equals the first divided by the second. Let us now develop the formula for this. We will use a subscripted small a for the coefficients of the quadratic equation, and a subscripted small k for those of the linear equation. Thus the equation describing the quadratic function fitted to the data is... 

Sodium bisulfite is often preferred in pyro developers and in Phenidone concentrates (Appendix 3 Pharmacopoeia Phenidone). Sodium bisulfite3 is often used in formulas that are divided into two solutions, as its weak acidity helps to inhibit the oxidation of the concentrated developing agent. When carbonate, contained in the B solution, is added to make a working solution, the bisulfite is immediately broken down into sulfite and bicarbonate, producing a useful buffering effect. 

A successful equivalent circuit approach to Wagner s theory was worked out by Hoar and Price. They developed a simple voltage divider circuit which gives quantitative formulas for emf and scaling rate that are very similar to those derived more rigorously by Wagner. A linear lumped version of their proposed circuit is shown in Fig. 3. The subscripts 1, 2 and 3 refer to M cations, X anions and electrons respectively. 

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