Color Chemistry and Computers (1985)

events of the past and present shape tomorrow our vital concern is you today's youth for our future depends on you before attempting to figure out where we're all going it is imperative for us to have a strong awareness of where we have been to untangle today's problems we need to understand yesterday this film series hopefully will in part make you aware of people places and events which have helped shape our nation and our world manufacturers hanover is pleased to sponsor this educational film manufacturer's hanover it's banking the way you want it to be [Music] [Music] we see colors all around us produced by nature by combinations of light and by chemistry as pigments dyes and in other forms [Music] in the past century scientific technology has filled the world with brilliant man-made colors most recently computer calculations can now predict color effects and other properties of a substance before it's even synthesized that is before it even exists in the real world this program explores these achievements in color chemistry [Music] color has always been a preoccupation of both artists and scientists in particular the goal of perfecting coloring materials is almost as old as art itself and much older than modern science [Music] the first dyes were taken from natural sources elderberries for instance [Music] or coca-neal a red dye made from ground up tropical insects [Music] until the 1850s dime was a static craft based largely on knowledge handed down over many generations [Music] only then did organic chemistry begin to reveal the structure of dye molecules groupings of atoms which produce coloring effects the first results were synthetic dyes invented to replace the natural ones indigo [Music] yellow brown [Music] and others [Music] a century ago this color wheel showed one company's range of synthetic dyes then available for dyeing silk in order to create better colorants scientists sought the precise relationship between the molecular structures of dyes and the colors they produced they also wanted precise ways to quantify or measure colors [Music] centuries before sir isaac newton showed that a prism split white light into its spectrum of component colors a major step in the scientific study of light and color a diffraction grating produces the same effect bands of colors which correspond to their wavelengths of light [Music] like the yellow wavelength produced by a sodium street lamp such devices led to the spectrophotometer which by determining the amount of light at different wavelengths transmitted by dyes and pigments gave precise color measurements a purple or technically violet dye for example absorbs mostly green light this trace shows the amounts of light absorbed the curve and its maximum define the dye's color the color we see is its transmitted complement red and blue making violet this dye absorbs mostly red leaving the complementary color blue green or cyan [Music] this dye absorbs mostly blue leaving red and green which combine to make yellow [Music] dye molecules were diagrammed and thought of as linked atoms in general the larger the dye molecule the bluer the color although it wasn't known why also adding small functional groups to a known dye molecule could alter coloring but again it wasn't known why [Music] nevertheless on this basis the orderly development of dye chemistry followed chemicals could at last be manipulated to produce colors with some consistency and the colors produced could be measured accurately such modern dyes are usually manufactured and sold as powders or liquids to be used as needed or they can be dyed or printed or transferred onto textile materials [Music] but many mysteries remained how could the coloring effects of possible dye molecules be predicted and how could the time and expense of developing new dyes be reduced the answers called for a deeper understanding of color chemistry recall our first example when the full color spectrum from a diffraction grating intersects a violet dye most green and some blue is absorbed but through what mechanism does this occur [Music] consider a dye solution in water and imagine you can see the individual molecules the violet dye molecules and water molecules would all be moving around at random let's look at one dye molecule atoms bound together with electrons at various energy levels surrounding them white light passing through the water solvent alone is unchanged but if white light intersects the dye molecule it emerges as violet light quantum chemistry which states that such subatomic events involve only fixed units of energy explains why this theory states that light takes the form of energetic particles called photons white light consisting of bundles of red green and blue photons which cause color sensations in the eye when white light intersects this particular dye molecule it's as if the green photons are somehow absorbed only red and blue ones emerge causing the eye to see the color purple this absorption is due to the fixed limited energy levels of the dye molecules shells of electrons consider this animation of the electron on the highest energy level quantum theory predicts that when the light photon interacts with this electron the green photons energy transfers the electron to a new higher energy level red and blue photon energies don't allow interactions they emerge and we see a combination of red and blue light violet light [Music] if this molecule stored the energy transferred to the electron it would eventually heat up and break up however the energy is actually lost to the solvent the molecule can then absorb more photons [Music] if the energy is released directly fluorescence occurs the quantum theory explained many color chemistry mysteries it also provided a way to compute the colorant and other properties of molecules even before they're synthesized that is before they even exist [Music] in computational quantum chemistry the molecule is first simplified only molecular bonds affecting the orbiting electrons are considered [Music] the remaining atoms are numbered [Music] the computer is then given a mathematical description of the molecule number of atoms number of electrons and much more the molecular bonds and the molecules geometry are all precisely described [Music] with these givens the computer can be used to solve a very complex equation the schrodinger equation which completely describes the molecule's properties [Music] approximate the probabilities of electrons being at various energy levels [Music] from these values it estimates how the electrons interact which gives a better description of the energy levels [Music] the calculation is repeated many times until no further improvement is possible [Music] this provides the molecules various energy levels in this case the difference between levels 7 and 8 determines the energy of the critical photons absorbed this photon energy level turns out to be 2.3742 electron volts which produces a light wavelength of 522 millimeters resulting in a violet color eventually the dye was synthesized and proved close to the predicted color the computer supplementing the laboratory experiments besides dying computational color prediction has been applied to improving analysis of unknown substances analytic chemistry developing pressure sensitive papers and films and finding new types of medical diagnosis [Music] such predictions have also been used to refine physical systems capable of color changes such as liquid crystals used in such modern displays as digital watches and electronic highway and airport signs application of computers to color chemistry is one more advanced in the scientific understanding of color processes the elusive subject that has been called painting with light [Music] manufacturers hanover has been pleased to sponsor this educational film manufacturer's hanover it's banking the way you want it to be