Welcome To View This project on Chemistry . This is a project on Chemistry. Chemistry doesn't only mean study of chemicals. It is also is an essential part of life. I have taken an interesting topic in Chemistry about “PHOTOGRAPHY”. Chemistry of Photography.
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This project on Chemistry
Step 5 Turn on the light for 15 seconds to expose the paper.Step 6 Develop the print (still in safety light) by placing it in the beaker containing the developer for 30 seconds (caution: use tongs), then the stop bath for 5 seconds, the fixer for 5 minutes and the deionized water wash for 5 minutes. While the paper is in the developer and stop bath, be certain that you agitate it by holding it with tongs and swishing about in the solution. Place the print on a papertowel to dry. Record the temperature of the developer, the Variac setting, and the exposure and developer times.Step 7 Try to improve the print. If it is too dark, reduce the exposure or the developing time. The exposure can be reduced by reducing the exposure time, raising the bulb or reducing the setting on the Variac. If the print is too light, the opposite remedies should be applied. Becertain to keep an accurate record of your conditions for each experiment. Your goal here is to find the conditions for the best print possible. You will use these conditions as a starting point in the subsequent sections for your developer.
Experiment 1: The Effect of Temperature on Reaction Rate
This experiment will focus on answering the question: What role does temperature play in the development of a photographic print? We can answer this question by actually developing a print in solutions with different temperatures.
Prepare developer, stop bath and fixer exactly as described in Section 1, Experiment 5 and Experiment 2. Assemble a controlled temperature bath for your developer solution as shown in the figure.
Next, expose three pieces of photographic paper for identical time intervals. Adjust the temperature of the developer in the inner beaker to exactly 25ºC by adding warm water or ice to the outer beaker. Develop, stop, fix and wash one contact print using your optimum times from Experiment 1. Record the time required for the appearance of the image on the print while it is in the developer solution.
Adjust the temperature of the developer solution to 15°C by adding ice to the outer beaker. Develop, stop, fix, and wash another print using the same times as above. Be certain the temperature does not vary by more than 1°C during the developing stage. Finally, adjust the temperature of the developer to 35°C. Repeat the development process as above.
What is the effect of the temperature change on the time for image formation and on the finished print? Explain. Chemists have a rule of thumb which states that "for every temperature increase of 10°C, the reaction rate doubles." Can you think of some way to test this rule on the reactions involved in development? In exposure?
An interesting modern innovation in photographic emulsion technology is related to the basic concept of silver halide grain geometry. In a classical silver halide crystal, typically a cubic crystal lattice, the structure will be relatively symmetrical in that the orientation of the crystal in the coated film will always present the same approximate surface area to be exposed. Extensive research efforts led to the development of grain precipitation processes that produced flatter "tablet" grains in which the crystals possessed a more asymmetric geometry, and in which a larger surface area was presented for exposure for the same given weight of silver halide (Fig. 2). That development resulted in significant improvements in film sensitivity and reductions in the amount of silver needed to obtain a given sensitivity – and a potentially important reduction in the cost of the film.