Flame test

The flame coloration, also called flame test is a method for analyzing chemical elements or ions thereof (detection reaction). The method is based on the fact that the elements or ions emit in a colorless flame light at specific wavelengths that is characteristic for each element. The flame color is produced by energy conversion from heat energy to radiant energy. The transformation comes about through valence electrons which are lifted by the heat energy in an excited state and back within the emission of light. Substances with which flame coloration is possible to see the pyrotechnics application due to this property.

In flame coloring the fabric sample is usually kept simple on a platinum wire or magnesia in the colorless flame of a Bunsen burner. Because of the color can now be inferred on the ions in the sample, however, the very intense yellow flame color of sodium often covers all other flame colors. With security can only be decided with the help of a spectroscope, which present elements in the sample, especially the flames staining of potassium and rubidium are quite similar, for example.

Distinguishing the flame color of the light output of the inert gases, based on an excited state, which is not brought on by electricity, by means of a flame.

Declaration of flame coloration

All elements emit light at high temperatures. However, for items that have a flame color, this already happens at the temperatures that prevail in a flame.

The outermost electrons of an atom are ( by burning will occur in this case) to a more distant from the nucleus, not occupied by electron energy level by supplying thermal energy - in an excited state - lifted. These electrons now have a higher potential energy. However, the negatively charged electrons usually fall in a split second back to the lower energy output energy level. The energy released when falling back energy is released as photons ( light particles). It is called a quantum. It is characterized by a well defined energy, and therefore with a single wavelength.

That these electrons fall back to lower energy energy levels can be done in stages. With each falling back to a lower energy of this electron energy level, there is now light at a specific wavelength (color), and thus a very specific energy decreases.

Color of the flame coloration

Arsenic, pale blue

Lead, pale blue

Boron, strong green

Calcium, brick

Potassium, violet

Copper, green, blue and

Copper sulfate, strong green

Lithium carmine

Sodium, yellow

Strontium, red

More flame colorations:

The shared light energy is dependent on the difference between the energy levels. This difference is different for each element. The energy of the photon determines its wavelength and thus the color.

If a member has a specific flame color on, then also have many connections to its ions, these flame coloration on (example: barium sulfate has a greenish flame coloration on, not barium ). Very many items send at high temperatures of visible spectral lines. Some items were even named after the color of their spectral lines observed in the flame color: Caesium (Latin: sky blue ), rubidium (Latin: dark red) and indium ( indigo blue spectral line ).

Use

The flame coloration can be used for the Beilstein test.

Modern techniques

Better ways than the classic flame color with the help of the eye provide the spectroscopic method of atomic spectroscopy, which represent a further development of this with the help of measuring instruments. The eye is here replaced by the spectrometer much better resolves the location of the spectral lines, as well as the non-visible regions of the electromagnetic spectrum depending on Spektroskopieart (e.g., IR or UV / VIS - spectroscopy) used for analysis. Additionally, the spectrometer is far better than the eye in a position to determine the strength of the spectral lines, whereby a quantitative analysis is possible.

Borate Atomic nucleus Antimony Quantitative analysis (chemistry)
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