Paper developers

Sing (see Ref. 207 and earlier papers) developed a modification of the de Boer r-plot idea. The latter rests on the observation of a characteristic isotherm (Section XVII-9), that is, on the conclusion that the adsorption isotherm is independent of the adsorbent in the multilayer region. Sing recognized that there were differences for different adsorbents, and used an appropriate standard isotherm for each system, the standard isotherm being for a nonporous adsorbent of composition similar to that of the porous one being studied. He then defined a quantity = n/nx)s where nx is the amount adsorbed by the nonporous reference material at the selected P/P. The values are used to correct pore radii for multilayer adsorption in much the same manner as with de Boer. Lecloux and Pirard [208] have discussed further the use of standard isotherms. 

Part I of the paper develops an exact variational principle for the ground-state energy, in which the density (r) is the variable function (i.e. the one allowed to vary). The authors introduce a universal functional F[n(r)] which applies to all electronic systems in their ground states no matter what the external potential is. This functional is used to develop a variational principle. 

Use the paper developed by the EPA (see footnote 27) to describe the phenol-formaldehyde runaway reactions that occurred between 1988 and 1997. 

Paper chromatography has been used to separate and detect pseudoephedrine hydrochloride from other pharmacologically active amines. Whatman No. 1 paper developed in n-butanol water 95% acetic acid (4 5 1), n-butanol toluene water 95% acetic acid (10 10 5 5), ethyl acetate water 95% acetic acid (3 3 1), or chloroform water 95% acetic acid (10 5 4) gave Rf values of 0.73, 0.35, 0.57, and 0.52 for pseudoephedrine hydrochloride respectively. Visualization of pseudoephedrine hydrochloride was done by spraying the chromatogram with 0.5% bromcresol green in methanol or 0.2% nin-hydrin in acetic acid butanol 5 95.30... 

We therefore suggest that Electron-Cloud radii 3 should be considered independently of structural radii the rest of this paper develops this idea. 

In this part of the paper, development of processes is summarized on the following simple classification of products ... 

Chem. 217 395, 1955. One of a series of papers developing kinetic techniques for elucidating the sequence of electron carriers in the respiratory chain. 

M. W. Evans et al., AIAS group paper, Development of the Sachs theory of electrodynamics, Optik (in press). 

In parallel to the development of the GSCTF, the CCFAC discussed and decided on which contaminants are considered immediately to comply with the criteria. This is being done through discussions based upon Discussion or Position Papers developed by one, or a few, delegations, which have a particular expertise or experience with the contaminant concerned. The GSCTF contains provisions concerning the content of such papers. If the CCFAC deems it appropriate, a draft standard is to be developed. In order to have a sufficient toxicological basis, the JECFA will be asked to assess the contaminant, if there is not already a recent JECFA evaluation available. 

What promises to be a valuable and time-saving method has been developed by Bayly and Bourne.22 The oligosaccharides are reacted with benzylamine, directly on the paper. Development of the A-benzyl-A-glycosylamines is then carried out, using 1-butanol-ethanol-ammonia-water mixtures. In a typical separation, the derivatives of malto-... 

The seventh and final paper, "Development of a Fermentation-Based Process for 1,3-Propanediol Highlights of a Successful Path from Corn to Textile Fiber," by Tyler Ames of DuPont, reviewed the multiyear effort by DuPont and its development partners (Genecor International and Tate Lyle) to commercialize a new biocatalytic process for the production of 1,3-propanediol (PDO), a key ingredient in DuPont s new Sorona advanced polymer platform. PDO is currently being produced at pilot scale at Tate Lyle s Decatur, IL, site, and construction of a commercial-scale facility is expected to begin soon. 

Developing agents for film can be used for paper and vice versa. In practical terms, some developing agents are more advantageous to use in one process than another. For example, ppd is better suited for film development than for paper development, while chlorhydroquinone is better suited for paper than film. Hydroquinone, metol, ascorbic acid, and Phenidone are well suited for either film or paper. This is an additional reason they are preferred by manufacturers. It is worthwhile to familiarize yourself with the brief description of each developing agent in Appendix 3 Pharmacopoeia. 

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. 

Restrainers are necessary to prevent excess fog. With film developers, this primarily means chemical fog. With paper developers, restrainers are used to retard both chemical and safelight fog. 

Whereas a degree of base fog is permissible in a negative, no amount of fog, which would show up as gray highlights, is acceptable in paper. For this reason, paper developers always require restrainer, often in significant amounts. 

Bromide is generally used in paper developers when a warm or neutral tone is desired. The more bromide, the warmer the tone, though too much bromide will inhibit development in the shadow areas and fogging may occur. 

It is advisable with all old paper, even those not exhibiting fog, to keep development times between 45 seconds and 1.5 minutes (the longer paper develops, the more likely it will exhibit fog). 

Compare each print to the test print and become familiar with the results. You can repeat this test with any paper developer. Doing this test in its entirety will familiarize you with the full range of effects and controls possible with any developer. It will also help you learn how to create your own formulas. 

Some readers may conclude that I have it out for JOBO rotary processors. Not at all. I highly recommend them for use with all color processes, C-41, E6, Ilfochrome, etc. They are also fine to use for paper development and negatives larger than 4X5 inches as long as sufficient volume of developer is maintained. They should never be used with developers that contain pyrogallol or pyrocatechin. 

Using Sodium Sulfate With D-72 or D-76 By adding sodium sulfate, anhydrous, to Kodak D-72 paper developer or Kodak D-76 film developer, as in the following table, the normal development time recommended for 68F/20C can be maintained through the range of temperatures shown. After adding the sulfate to the developer solution, stir until dissolved completely. 

To increase the flexibility of MQ and PQ print-developing formulas, keep a bottle of carbonate solution and a bottle of 10% bromide on your darkroom shelf. I learned this trick from photographer Edna Bullock, who learned it from her husband, Wynn Bullock. Wynn used this technique with Ethol LPD paper developer. 

Adding carbonate solution to paper developer will increase the speed of the developer and create the appearance of greater contrast through stronger and richer blacks. Start with... 

Changes and variations in image tone may not always be as glaringly apparent. Often the difference is subtle, so much so that someone viewing a print might not even be aware that it is neutral, cool, or warm, unless the fact is drawn to their attention, or they see an example of each, side-by-side. The simplest test to determine whether or not a paper is cold-, warm-, or neutral-toned, is to develop it for two minutes in a neutral tone developer such as D-72 and compare it to other papers developed similarly. If a paper is warm- or cold-toned the color can be seen in the shadows. 

Method 1. The classic developing agent for creating cold tones on bromide papers is amidol. However, PQ developers using organic antifoggant, such as benzotriazole, will also increase the amount of cold image tone in a print (Formulas Paper Developers, Blue-Black Developer). In either case the results are usually very subtle. 

All three of the famous Westons—Edward, Brett, and Cole—used amidol paper-developing formulae. All three were famous for their rich blacks and full-scale print tones. All three used different amidol formulae. There is some confusion as to the formula each one used, and more than one has surfaced for Brett and Edward. It may be possible that they used different formulae during the course of their long careers. 

Develop, stop, and fix the test strip for your normal paper development time. 

The paper developer affects the results. If you develop in glycin or pyrocatechin, the blue tones will be lighter. Any developer that produces a brownish color by direct development is good for... 

Until the advent of 35 mm film, with the resulting emphasis on fine-grain developers, glycin was used mainly in paper developers. Now it is sometimes used in combination with other developing agents for fine-grain film development. 

Notes Potassium carbonate can be substituted for sodium carbonate as an alkali accelerator in developers. As its solubility is much greater, developers with greater concentration can be formulated. Thirteen parts by weight are equal to 10 parts by weight of sodium carbonate. Substituting potassium carbonate for sodium carbonate will help to obtain warmer tones in paper development. 

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