edited by
GEORGE L. GILBERT Denisan University Granville, Ohio 43023
A Demonstration of Color Developmenk Formation of the Subtractive Primary Dyes Edwin S. Olson South Dakota S t a t e University Brookings, 57007 Checked by: Wayne L. Smith and Robert L. Sundberg Colby College Wateruille, Maine Several excellent reviews of color development are available;' however, I wish to report a method for demonstrating the Kodachrome process in alectwe situation. I normally use this demonstration in the latter part of a one-year organic course as an illustration of carbanion formation and attack on an electrophile (oxidized developer). Thus the coupling reactions are written out and ex~lainedafter comnletion of the demonstration, and these reactions then serve as a colorful wav to eet into the malonic ester svnthesis. ete. The basic idea in the dkmonstration is to carry 01%the d i e forming reactions in s e ~ a r a t beakers e to r e ~ r e s e nthe t three lavers of film and thentransfer the dye sol;tions with filtration to Petri dishes which can be stacked and exhibited usine an overhead nrojector. After briefly explaining the 3-layercomposition of the film and the sensitivities of each laver. . . I first carrv throueh an exanlple whrre hlue light exposes the beakers representing the film, then later show how theother ~rimarvadditivecolors can he obtained in the image. T o represent the production of a blue image from exposure to blue light, four beakers are used, two for the first (A) layer and one each for the second (B) and third (C) layers. These contain 15 ml of 95% ethanol. I explain that blue light has exposed the blue-sensitive silver halide granules in the image area of the A layer. To represent the activationof the granules, I add a few drops of 10% aqueous silver nitrate to one of the A beakers. Then I add a few drops of developer solution (a 2% aqueous solution of Part D of the E-4 Kodak processing kit21 and two drops of 40% NaOH solution which produces a dark silver precipitate representing the negative image. I explain that this protects the latent image from further development while the color reversal process is carried out, and that the other lavers and the nonimaee area of A have not vet been exposed and the sul~tractiveprimary colors will form in theie lavers in this wocess.The denlunstmtim thus nroceeds in the s a k e order a; the Kodachrome process, i.e., f i k t the exposed areas (in the first (A) laver in the blue lieht e x a m' ~ l ebeine" used), then the uonexposed C, A, and f3 layers. Nrxt the red expmure from thr rrwrse side which activates the panules in layer C isexplained. Two milliliters of the cyan cuupler solution (5% alcohohc solution of r)henol) are added to the C beaker, followed by 1ml of the developer solution and Submitted by:
two drops of 40% NaOH solution. Then three drops of the silver nitrate solution are added to represent the exposed granules. The resulting cyan dye solution is filtered through a cone into a flask and the filtrate is poured into a Petri dish. The blue exposure from the top side, which activates the nnnima~earea of laver A. is ex~lained.Two ml of the vellow coupler~olution(5ialcoholic acetoacetilnilide soluti&) are added tn the second A heaker, then 1 ml of developer solution, then the silver nitrate sdution. and 2 drops of NaOH s
