Color of flame

The focus of this section is the emission of ultraviolet and visible radiation following thermal or electrical excitation of atoms. Atomic emission spectroscopy has a long history. Qualitative applications based on the color of flames were used in the smelting of ores as early as 1550 and were more fully developed around 1830 with the observation of atomic spectra generated by flame emission and spark emission.Quantitative applications based on the atomic emission from electrical sparks were developed by Norman Lockyer (1836-1920) in the early 1870s, and quantitative applications based on flame emission were pioneered by IT. G. Lunde-gardh in 1930. Atomic emission based on emission from a plasma was introduced in 1964. 

An example of a military use is the Navy Light MK 1 Mod I (See Fig). This device is designed to produce a bright light for recognition and signalling purposes. The Mod number indicates the different colors of flame pro-... 

If the color of flame.is. violet, the salt is fairly pure(Ref l,p 141 Ref 3,p 862). K can be identified by pptg it as K2NaCo(N02)g, as well as by potassium salts of chloro-platinate, perchlorate) acid tartrate, picrate, silicofluoride, etc(Ref 3,p 862). Various quantitative methods for detn of K ion are given in Refs 3,4,4a 8... 

The existence of these different practices was not sufficient to create a discipline or subdiscipline of physical chemistry, but it showed the way. One definition of physical chemistry is that it is the application of the techniques and theories of physics to the study of chemical reactions, and the study of the interrelations of chemical and physical properties. That would mean that Faraday was a physical chemist when engaged in electrolytic researches. Other chemists devised other essentially physical instruments and applied them to chemical subjects. Robert Bunsen (1811—99) is best known today for the gas burner that bears his name, the Bunsen burner, a standard laboratory instrument. He also devised improved electrical batteries that enabled him to isolate new metals and to add to the list of elements. Bunsen and the physicist Gustav Kirchhoff (1824—87) invented a spectroscope to examine the colors of flames (see Chapter 13). They used it in chemical analysis, to detect minute quantities of elements. With it they discovered the metal cesium by the characteristic two blue lines in its spectrum and rubidium by its two red lines. We have seen how Van t Hoff and Le Bel used optical activity, the rotation of the plane of polarized light (detected by using a polarimeter) to identify optical or stereoisomers. Clearly there was a connection between physical and chemical properties. 

Robert Bunsen and Gustav Kirchhoff, whom we encountered in passing in the previous chapter, took a major step in this direction in the middle of the nineteenth century. Bunsen moved to Heidelberg in 1852, and there he worked on combustion. Kirchhoff joined Bunsen two years later. It was Kirchhoff the physicist who suggested to Bunsen the chemist that a prism would be useful to examine the color of flames as they were affected by different metallic salts. 

Color of Flame Crimson Yellow Violet Red Blue... 

In 1823, Herschel [15] in the Transactions of the Royal Society of Edinburgh published his observations of the colors of flames produced by the introduction of alkaline earth salts. The green color obtained with barium salts is due to BaOH and the reddish color characteristic of strontium salts is caused by SrOH. The red colors of fireworks can also be attributed to emission from SrOH [16]. It was not until the 1950s that modern flame studies [17, 18] identified the molecules that are responsible for the alkaline earth flame colors. In contrast to the alkaline earths, the flame colors of the alkali elements are produced by atomic emission. The formation of molecules such as CaOH and SrOH, in fact, greatly complicates the use of flame absorption and emission for the determination of the concentrations of alkaline earth elements in analytical chemistry. 

Do the colors of flame tests result from taking in energy or releasing energy ... 

Polymer Color of Flame Odor of Vapor Other Notable Points... 

TABLE 9.A.3 Colors of Flames Produced by Various Solutions of Ionic Solids. 

This is a spectacular experiment that demonstrates the color of flames emitted from various metal atoms, which are the same colors made by sodium street lamps and many fireworks. The colors of flames are characteristic of the metal (or metal ion) and can be used to identify the metal and/or detect its presence in the solution. This constitutes spectroscopy with the naked eye. 

Chemiluminescence is, in a general sense, the opposite of photodissociation. Here a molecule is formed in an excited state by means of chemical reaction. The new species then fluoresces to deexcite. It is the process which accounts for the characteristic colors of flames. An example is found in the combustion of CO where atomic oxygen is produced, most likely as the first step in the oxidation of CO. Then the following sequence of reactions occurs ... 

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