Flame coloration tests

Atomic spectroscopy refers to a wide range of techniques that are applied to materials that have been reduced to atomic or ionic forms or species in an electric arc, flame, or plasma. When one speaks of atomic spectra, molecules and compounds that have been of discussion up to now are no longer an issue. AS is in fact a monumental extension and improvement upon the flame color tests that were mentioned at the beginning of this article. 

Mineral identification is also sometimes possible on the basis of specific physical characteristics such as density, hardness, streak, or by flame coloration tests, microcosmic bead colors, or blowpipe tests. These methods are seldom of general applicability, but they may be useful in particular circumstances. 

VFO works well in gas turbines. In a nine-month test program, the combustion properties of VFO were studied in a combustion test module. A gas turbine was also operated on VFO. The tests were conducted to study the combustion characteristics of VFO, the erosive and corrosive effects of VFO, and the operation of a gas turbine on VFO. The combustion tests were conducted on a combustion test module built from a GE Frame 5 combustion can and liner. The gas turbine tests were conducted on a Ford model 707 industrial gas turbine. Both the combustion module and gas turbine were used in the erosion and corrosion evaluation. The combustion tests showed the VFO to match natural gas in flame patterns, temperature profile, and flame color. The operation of the gas turbine revealed that the gas turbine not only operated well on VFO, but its performance was improved. The turbine inlet temperature was lower at a given output with VFO than with either natural gas or diesel fuel. This phenomenon is due to the increase in exhaust mass flow provided by the addition of steam in the diesel for the vaporization process. Following the tests, a thorough inspection was made of materials in the combustion module and on the gas turbine, which came into contact with the vaporized fuel or with the combustion gas. The inspection revealed no harmful effects on any of the components due to the use of VFO. 

Hame tests fur Na (yellow) and K+ (violet). A drop of solution is picked up on a platinum loop and immersed in tire flame. The test for K+ is best done with a filter that hides the strong Na+ color. 

Analysis. Ca gives a brick-red flame coloration, indicating that various optical spectroscopies will be effective in its determination. Ca is quantitatively determined by colorimetry down to 100 ppb using murexide or o-cresolphthalein, by atomic absorption spectroscopy (AAS) to 20 ppb, to 1 ppb by electrothermal absorption spectroscopy (ETAS), to 0.01 ppb by inductively-coupled plasma emission spectroscopy (ICPES), and to 10 ppb by inductively-coupled plasma mass spectroscopy (ICPMS). A spot test for Ca which extends to 3 ppm is provided by glyoxal bis(2-hydroxyanil). 

Anaiysis. If a borate is treated with H2SO4 and methanol H3COH, methyl borate is produced. If a small amount of the mixture is introduced to a flame, a green flame color is produced. The test is sensitive to 20 ppm of B. Ba and Cu interfere, both of these also giving a green color. A spot test with curcumin will detect 5 ppm of B. Titration of H3BO3 in a mannitol solution... 

Certain nitrogenous compounds, however, give a volatile cuprous cyanide in this test which produces a green flame coloration. The presence of halogen must therefore be confirmed by other tests. 

FIGURE 24.7 (See color insert following page 530.) Flame spread test of PP using BS 5438 Test 1 rig. 

The flame coloration and the spectrum (p. 54) afford delicate tests for the presence of lithium. From solutions which are not too dilute it can be precipitated as phosphate, fluoride, or carbonate. Like sodium, it yields an antimonate of slight solubility, but in contradistinction to potassium its platino-chloride and hydrogen tartrate are soluble. 

All sodium salts impart a characteristic yellow coloration to the Bunsen flame, the test being so delicate as to detect 3xl0-10 grams. The extreme delicacy of the test and the wide distribution of traces of sodium chloride throughout the atmosphere render the persistence or otherwise of the coloration an important factor in determining the presence or absence of sodium in the substance under examination. In the spectroscope, sodium gives a yellow line, coincident with the D-line of the solar spectrum. 

Identifying patterns For three of the metal ions tested, explain how the flame color you saw relates to the lines of color you saw when you looked through the spectroscope. 

Designing experiments During a flood, the labels from three bottles of chemicals were lost. The three unlabeled bottles of white solids were known to contain the following substances strontium nitrate, ammonium carbonate, and potassium sulfate. Explain how you could easily test the substances and relabel the three bottles. (Hint Ammonium ions do not provide a distinctive flame color.)... 

The presence of halogens can be demonstrated by the Beilstein Test. A small amount of the sample is placed on a copper wire and burned in the Bunsen flame. The copper halide which forms imparts a green color to the flame. This test, though sensitive, must be conflrmed through fusion and detection by means of silver halide. 

The vapor of certain chemical elements imparts a characteristic color to the flame of burning gas (e.g., Bunsen burner). This property is used for identifying quahtatively various metallic elements. The flame coloration is caused by electronic transitions occurring between the energy levels of the atoms of the chemical element. For a particular chemical element the flame coloration is always the same, regardless of whether the chemical element is in the free atomic state or chemically in molecules. For example, free sodium metal, sodium chloride, sodium carbonate and sodium sulfate all impart an intense yellow color to the flame (D-line of 589 nm). This yellow color is characteristic of sodium in any form, and hence can be used as a test for sodium. In the making of flame tests, chlorides of the metals are commonly used, since chlorides are more volatile than other salts. 

This flame color is specific for tin. The test may be carried out on a single drop of the solution, in which case the reducing power of the gases of the flame is sufficient. The presence of arsenic, if more than equivalent to the amount of tin, causes this very characteristic reaction to fail. Hydrated metastannic acid, prepared in the wet way and ignited, responds decisively to this test, but native tinstone (cassiterite) does not. 

Objective Identify the compounds with the help of their characteristic frequencies and the correlation charts. Spectrum 1-B belongs to a compound which gave a positive Prussian blue precipitate (color test for the presence of nitrogen). Spectrum 19-B belongs to a compound which gave a positive Beilstein test (flame test for chlorine—green). It is an extremely reactive material when in contact with moist air. 

Sodium is identified by the intense yellow color that sodium compounds impart to a flame or spectroscopically by the characteristic sodium lines. The latter test is extremely sensitive, yet because many materials contain traces of sodium salts as impurities, it is not conclusive evidence of the presence of sodium in any considerable quantity. 

There is the possibiUty of a chemical reaction between a plastic and a colorant at processing temperatures. Thermal stabiUty of both the polymer and colorant plays an important role. Furthermore, the performance additives that may have been added to the resin such as antioxidants, stabilizers, flame retardants, ultraviolet light absorbers, and fillers must be considered. The suitabiUty of a colorant in a particular resin must be evaluated and tested in the final apphcation after all processing steps to ensure optimum performance. 

Uses, (see also under Perchlorate Propellants and Explosives). It is used in pyrotechnics to impart a bright red color to flames (Ref 3). A gel was made from 50g of Sr perchlorate, lOOg of me ale, and 4.6g of Carbopol 940 gelling agent. Five g of this gel burned for 10 mins with an intense red flame (Ref 11). A 66/34 mixt of Sr perchlorate/powd Al was tested as a photo-flash compn for both sea level and high altitude use (Ref 8). Another mixt of 50ml of me... 

The need to paint the blends has also resulted in new painting systems. Recently, a nonpolar color coat based on a hydrogenated polybutadiene diol and melamine resin for TPO bumper fascia was invented. The breakthrough technology allows the elimination of the TPO pretreatment step such as adhesion promoter, flame, or plasma during manufacturing. The paintability of two different types of E-plastomers was evaluated. The olefinic white paint was found to provide excellent paint adhesion for both types of metallocene plastomers. Paint peeling was not observed in any of the test... 

Both LiCl and KC1 are soluble in water, but Li3P04 is not very soluble. Hence the addition of K3P04(aq) to a solution of the white solid will produce a precipitate if the white solid is LiCl, but no precipitate if the white solid is KC1. The best method is a flame test lithium gives a red color to a flame, while the potassium flame test is violet. 

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