Haven’t you seen me in Paints?
In 1856, at the age of 18, William Henry Perkin set out with idea of making quinine by oxidizing allytoluidine –instead he accidentally produced the synthetic dye, mauve, a derivative of coal tar with an aniline base.
I can be present in the form of paints or dyes emitting the ‘glow’ that you so marvel at. When I am present in such paints, they are called fluorescent paints.
Fluorescent paints offer a wide range of pigments and chroma which also ‘glow’ when exposed to the long-wave “ultraviolet” frequencies (UV). These UV frequencies are found in sunlight and some artificial lights. But they and their glowing-paint applications are popularly known as Black Light and ‘black-light effect’, respectively.
There are both visible and invisible fluorescent paints. The visible appear under white light to be any bright colour, turning peculiarly brilliant under black lights. Invisible fluorescent paints appear transparent or pale under daytime lighting, but will glow only under UV light and in a limited range of colours. Since these can seem to ‘disappear’, they can be used to create a variety of clever effects.
Both types of fluorescent painting benefit when used within a contrasting ambience of clean, matte-black backgrounds and borders. Such a “black out” effect will minimize other awareness, and cultivating the peculiar luminance of UV fluorescence. Both types of paints have extensive application where artistic lighting effects are desired, particularly in “black box” entertainments and environments such as theatres, bars, shrines, etc. Out-of-doors however UV wavelengths are rapidly scattered in space or absorbed by complex natural surfaces, dulling the effect. Furthermore, the complex pigments will degrade quickly in sunlight.
Fluorophores
Then followed a series of compounds which added to the list where my prevalence was noteworthy.
H. Caro (1874): eosin
C. Liebermann (1880): polycyclic aromatic hydrocarbons
Paul Erlich (1882) used uranin (the sodium salt of fluorescein) to track secretion of the aqueous humour in the eye. First in vivo use of fluorescence.
K. Noack (1887) published a book listing 660 compounds arranged according to the colour of their fluorescence.
Now, there had to be the classification of compounds and chemical groups having me as a strong property in them. So, R. Meyer (1897) used the term “fluorophore” to describe chemical groups which tended to be associated with fluorescence; this word was analogous to “chromophore” which was first used in 1876 by O.N. Witt to describe groups associated with colour.
In 1867, F. Goppelsröder introduced the term form “Fluoreszenzanalyse” and performed the first fluorimetric analysis in history: the determination of Al(III) by the fluorescence of its morin chelate.
Could one have imagined that one of the first uses of fluorescein could be found from ground-water? In 1877, in a major ground-water tracing experiment in southern Germany, it was found that River Danube and Rhine are connected by underground streams. I was placed in the form of Fluorescein in the Danube and about 60 hours later I appeared as an affluent in the Rhine. 10 Kilograms of fluorescein were used!
