Thursday, December 16, 2010

analytical chem

How to Interpret the Results
The sample is identified by comparing the observed flame color against known values from a table or chart.
Red
Carmine to Magenta: Lithium compounds. Masked by barium or sodium.
Scarlet or Crimson: Strontium compounds. Masked by barium.
Red: Rubidium (unfiltered flame)
Yellow-Red: Calcium compounds. Masked by barium.
Yellow
Gold: Iron
Intense Yellow: Sodium compounds, even in trace amounts. A yellow flame is not indicative of sodium unless it persists and is not intensified by addition of 1% NaCl to the dry compound.
White
Bright White: Magnesium
White-Green: Zinc
Green
Emerald: Copper compounds, other than halides. Thallium.
Bright Green: Boron
Blue-Green: Phosphates, when moistened with H2SO4 or B2O3.
Faint Green: Antimony and NH4 compounds.
Yellow-Green: Barium, manganese(II), molybdenum.
Blue
Azure: Lead, selenium, bismuth, cesium, copper(I), CuCl2 and other copper compounds moistened with hydrochloric acid, indium, lead.
Light Blue: Arsenic and come of its compounds.
Greenish Blue: CuBr2, antimony
Purple
Violet: Potassium compounds other than borates, phosphates, and silicates. Masked by sodium or lithium.
Lilac to Purple-Red: Potassium, rubidium, and/or cesium in the presence of sodium when viewed through a blue glass.
Limitations of the Flame Test
  • The test cannot detect low concentrations of most ions.
  • The brightness of the signal varies from one sample to another. For example, the yellow emission from sodium is much brighter than the red emission from the same amount of lithium.
  • Impurities or contaminants affect the test results. Sodium, in particular, is present in most compounds and will color the flame. Sometimes a blue glass is used to filter out the yellow of sodium.
  • The test cannot differentiate between all elements. Several metals produce the same flame color. Some compounds do not change the color of the flame at all.
Primary Reference: Lange's Handbook of Chemistry, 8th Edition, Handbook Publishers Inc., 1952.

Flame Test Colors

Symbol Element Color
As Arsenic Blue
B Boron Bright green
Ba Barium Pale/Yellowish Green
Ca Calcium Orange to red
Cs Cesium Blue
Cu(I Copper(I) Blue
Cu(II) Copper(II) non-halide Green
Cu(II) Copper(II) halide Blue-green
Fe Iron Gold
In Indium Blue
K Potassium Lilac to red
Li Lithium Magenta to carmine
Mg Magnesium Bright white
Mn(II) Manganese(II) Yellowish green
Mo Molybdenum Yellowish green
Na Sodium Intense yellow
P Phosphorus Pale bluish green
Pb Lead Blue
Rb Rubidium Red to purple-red
Sb Antimony Pale green
Se Selenium Azure blue
Sr Strontium Crimson
Te Tellurium Pale green
Tl Thallium Pure green
Zn Zinc Bluish green to whitish green

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