do not match. these colors are basically the same as the colors seen when using darkfield dispersion staining. the double aperturing of this method enhances the color effect but also sacrifices resolution of the particles. in fields of view where particles may be stacked or in very close proximity it may be difficult to be sure which small particle is actually producing the color. examples of this type of dispersion staining and the colors shown for different λo's can be seen at the microlabgallery.com site for objective stop dispersion staining. this method is more difficult to interpret due to the single color rather than two bracketing colors but is relatively accurate near the center of the visible range. historical development isaac newton demonstrated that “white” light was actually composed of many different “simple” colors and that materials had different optical properties depending on which of the simple colors was being used to measure them. he demonstrated these facts with a series of experiments using one or more prisms. the difference in the optical properties of materials as a function of the “simple” or monochromatic colors of light is called dispersion. he was also the first person to note that different materials had different dispersion properties. “sulfurous” liquids (organic liquids) had a higher refractive index than was expected based on their specific gravity and had a steeper dispersion curve than most solids. these well documented observations would take just over two centuries to become an analytical technique. the first paper documenting dispersion effects seen through the microscope was written in 1872 by o. maschke in germany. this paper discussed the occurrence of colored becke` lines when a particle was in a liquid of matching refractive index. prior to this paper these colors were thought to be the result of the microscope lenses (chromatic aberration) and not the result of the slide mounted subject and the medium in which it was mounted. in 1884 and 1895 christian christiansen published his data on the first analytical application of dispersion colors, the christiansen filter. he found that by placing a colorless transparent powder into a vial of a colorless organic liquid he could create monochromatic light from white light if the liquid and powder had the same refractive index for just that wavelength. only that wavelength would see an optically homogeneous media and pass directly through the vial. the other wavelengths would be scattered in all directions by the particles in the liquid. monochromatic light could be viewed by looking through the vial along the path of the direct beam of light. at any other angle the complementary color of that wavelength would be observed. if he chose a liquid that matched the refractive index of the powder in the far red, 700 nanometers wavelength, he could create any other wavelength by heating the vial, thereby changing the wavelength at which the powder and liquid's refractive index matched. this technique did not work for any powder or liquid. for optimal effects the powder and the liquid had to be carefully selected so that the intersection of their dispersion curves created as large an angle as possible over the full range of visible wavelengths. christiansen's interest was in the creation of monochromatic filters and not the development of an analytical technique. it wasn't until 1911 that the analytical potential of dispersion effects was reported by f. e. wright. he observed that the colored becke` lines noted by maschke could be used to distinguish between two materials with the same refractive index but different dispersion curves. the colors could also indicate the region of the visible light spectrum for which a particle and liquid it was mounted in had a refractive index match. wright also noted that by using oblique transmitted illumination the particle would show these colors without having to inspect the becke` line. the technical literature had little additional discussion of dispersion effects until 1948. that year s. c. crossmon, n. b. dodge, and co-authors r. c. emmons and r. n. gates all wrote papers on the use of dispersion effects through the microscope to characterize particles. crossmon seems to have coined the term “dispersion staining” as any optical technique that used the “christiansen effect” to produce color in the image of colorless particles. he demonstrated the use of becke` line, oblique illumination, darkfield, and phase contrast dispersion staining methods. s. c. crossmon and w. c. mccrone have published numerous papers on the use of objective back focal plane stop dispersion staining techniques since that time. yu. a. cherkasov published an excellent paper on this topic in 1958 and it was translated into english in 1960. well over 100 papers have been written on the various methods of dispersion staining and their application since about 1950 and most of these since 1960. in spite of the early work done on this technique it was not until the 1950s that it became generally known among microscopists. it is now recognized as a powerful tool in the characterization of materials and the detection of low level contaminants. it has demonstrated sensitivity for particle contaminants in powders down to the parts per million. the dispersion of the refractive index is a fundamental property of matter. it may be thought of as the result of the relative proximity of the harmonic frequencies of the outer shell electrons in a compound to the frequencies of visible light. the harmonic frequency of the bonding electron is the result of the energy of that bond. if the bond is very strong the frequency will be very high. the higher the frequency the less effect the difference in frequencies from blue to red will have on the refractive index. for the relatively high energy bonds in most inorganic solids this means their refractive indices change very little over the visible range of frequencies. the refractive indices of organic compounds on the other hand, with their lower bonding energies, change significantly over the visible range. this difference in dispersion is the basis of the christiansen effect and the dispersion staining methods. notes and references "archived copy" (pdf). archived from the original (pdf) on 2008-12-17. retrieved 2008-07-19.: cs1 maint: archived copy as title (link) us-epa bulk asbestos test method 600/r-93/116 page 16 "archived copy" (pdf). archived from the original (pdf) on 2008-10-07. retrieved 2008-07-19.: cs1 maint: archived copy as title (link) us-niosh bulk asbestos test method 9002, pages 4 and 5 us-osha bulk asbestos test method d-191, section 4.6 kohlbeck, j.a. and w.t. bolleter, “microscopic determination of the degree of nitration of nitrocellulose with dispersion staining”, journal of applied polymer science, vol 12, no.1, pp. 131-135, 1968 su, shu-chun, “dispersion staining - a versatile complement to becke line method for refractive index determination”, geochimica et cosmochemica acta supplement, vol. 69, issue 10, supplement 1, goldschmidt conference abstracts 2005., p.a727, 2005 us-fbi method for characterizing trace glass evidence characterizing the chemical composition of the mineral olivine crutcher, e. r., “optical microscopy: an important tool for particulate receptor source apportionment”, proceedings of the air pollution control association, page 272, 1981. this paper includes dispersion staining as part of the body of methods used to identify the sources of air pollution in urban environments. crutcher, e. r., “the role of light microscopy in aerospace analytical laboratories”, proceedings of the ninth space simulation symposium, 1977. this paper includes dispersion staining as part of the body of methods used to identify the sources of contamination in aerospace or micro-electronic clean rooms. hoidale, “the color identification of transparent crystalline particles with an optical microscope: a literature survey of dispersion staining”, g. b., u.s. army microfiche, ad 603 019, p. 1, 1964 wright, f. e., the methods of petrographic-microscopic research”, carnegie institution of washington, publication no. 158, pp. 92-98, 1911 crossmon, germain c., “microscopical distinction of corundum among its natural and artificial associates: employing the christiansen effect by transmitted, dark-field illumination”, analytical chemistry, vol. 20, no. 10, pp.976-977, oct. 1948 crossmon, germain c., “ dispersion staining with phase contrast microscopy accessories: the microscopic identification of quartz”, science, vol 110, p. 237, 1949 cherkasov, yu. a., “application of ‘focal screening’ to measurements of indices of refraction by the immersion method”, trans. by ivan mittin, international geological review, vol. 2, pp. 218-235, 1960. newton, isaac, opticks, dover publications reprint of the 4th edition of the 1704 book by newton, 1979 hoidale, glen b., “the color identification of transparent crystalline particles with an optical microscope: a literature survey of dispersion staining”, u.s. army microfiche, ad 603 019, p. 1, 1964 wright, f. e., the methods of petrographic-microscopic research”, carnegie institution of washington, publication no. 158, pp. 92-98, 1911 crossmon, g. c. “microscopical distribution of corundum among its natural and artificial associates”, analytical chemistry, vol. 20, no. 10, 1948 dodge, nelson b., “the dark-field color immersion method”, american mineralogist, vol. 33, pp. 541-549, 1948 emmons, r.c. and r. m. gates, “the use of becke line colors in refractive index determination”, american mineralogist, vol. 33, pp. 612-619, 1948 crossmon, germain c., “ dispersion staining with phase contrast microscopy accessories: the microscopic identification of quartz”, science, vol 110, p. 237, 1949 cherkasov, yu. a., “application of ‘focal screening’ to measurements of indices of refraction by the immersion method”, trans. by ivan mittin, international geological review, vol. 2, pp. 218-235, 1960. bibliography brown, k. m. and w. c. mccrone, “dispersion staining”, the microscope, vol. 13, pp. 311 and vol. 14, pp. 39, 1963. cherkasov, yu. a., “application of ‘focal screening’ to measurements of indices of refraction by the immersion method”, trans. by ivan mittin, international geological review, vol. 2, pp. 218–235, 1960. crossmon, g. c. “microscopical distribution of corundum among its natural and artificial associates”, analytical chemistry, vol. 20, no. 10, 1948. crossmon, g. c., “the ‘dispersion staining’ method for the selective coloration of tissue.” stain technology, vol. 24, pp. 61-65, 1949. crossmon, g. c., “dispersion staining microscopy as applied to industrial hygiene”, american industrial hygiene quarterly, vol. 18, no. 4, pp. 341, 1957. crutcher, e. r., “the role of light microscopy in aerospace analytical laboratories”, proceedings of the ninth space simulation symposium, 1977. crutcher, e. r., “optical microscopy: an important tool for particulate receptor source apportionment”, proceedings of the air pollution control association, pp. 266–284 1981. dodge, nelson b., “the dark-field color immersion method”, american mineralogist, vol. 33, pp. 541–549, 1948 emmons, r.c. and r. m. gates, “the use of becke line colors in refractive index determination”, american mineralogist, vol. 33, pp. 612–619, 1948 hoidale, glen b., “the color identification of transparent crystalline particles with an optical microscope: a literature survey of dispersion staining”, u.s. army microfiche, ad 603 019, 1964. kohlbeck, j.a. and w.t. bolleter, “microscopic determination of the degree of nitration of nitrocellulose with dispersion staining”, journal of applied polymer science, vol 12, no.1, pp. 131–135, 1968. laskowski, thomas e. and david m. scotford, “rapid determination of olivine compositions in thin section using dispersion staining methodology”, american mineralogist, vol. 65, pp. 401–403, 1980 (available on-line at http://www.minsocam.org/ammin/am65/am65_401.pdf) mccrone, walter c., “dispersion staining”, american laboratory, dec., 1983. mccrone, walter c. and john gustav delly, the particle atlas, ann arbor scientific publishers, inc., ann arbor, michigan, 1973. newton, isaac, opticks, dover publications reprint of the 4th edition of the 1704 book by newton, 1979 schmidt, k. o., “phase contrast microscopy and dispersion staining”,staub, vol. 18, 1958. speight, richard g., “an alternative dispersion staining technique”, the microscope, vol. 25, 1977. schmidt, k. 8., “phase contrast microscopy in the particle laboratory”, staub, vol. 22, 1962. su, shu-chun, “dispersion staining - a versatile complement to becke line method for refractive index determination”, geochimica et cosmochemica acta supplement, vol. 69, issue 10, supplement 1, goldschmidt conference abstracts 2005., p.a727, 2005 united states environmental protection agency (us-epa), https://web.archive.org/web/20081217074149/http://www.epa.gov/ne/info/testmethods/pdfs/epa_600r93116_bulk_asbestos_part1.pdf united states federal bureau of investigation (us-fbi), https://web.archive.org/web/20080723155043/http://www.fbi.gov/hq/lab/fsc/backissu/jan2005/standards/2005standards9.htm united states national institute for occupational safety and health (us-niosh), https://web.archive.org/web/20081007161605/http://www.cdc.gov/niosh/nmam/pdfs/9002.pdf united states occupational safety and health administration (us-osha), https://www.osha.gov/dts/sltc/methods/inorganic/id191/id191.html#sec46 wright, f. e., the methods of petrographic-microscopic research. their relative accuracy and range of application, pub. no. 158, carnegie inst., washington, 1911. optical microscopy microscope optical microscopy illumination andcontrast methods bright-field microscopy köhler illumination dark-field microscopy phase contrast quantitative phase-contrast microscopy differential interference contrast (dic) dispersion staining second harmonic imaging (shim) 4pi microscope structured illumination sarfus raman fluorescence methods fluorescence microscopy confocal microscopy multiphoton microscopy (two-photon, three-photon) image deconvolution total internal reflection fluorescence microscopy