Flame Tests

Flame tests may not be the most accurate, nor do they work for gold, but they can be really effective for other elements.  Boron is one that imparts a greenish color to a flame.  This gives rise to the story of how the 20 Mule Team Borax Company got started.  It seems a prospector who was down on his luck was prospecting Death Valley, California with his wife when he tried a flame test on some of the dried salts he found in the dessert.  It burned green so he turned to his wife and said, “She burns green Ma, we’re rich!”

A chemist performing a flame test on copper sulfate.  Notice the blue color of the flame.

Flame tests are conducted on a length of thin platinum wire that is first dipped in a dilute solution of hydrochloric acid then in the pulverized sample of the substance to be tested; then it is held into a hot flame.

Depending on the element contained in the sample it colors the flame various colors.  This technique will present a pretty accurate idea of what king of substance you have, but the accuracy of the test can be improves with a spectroscope.

Table 1 shows the colors of the flame test of various elements:

Symbol	Name	Color
As	Arsenic	Blue
B	Boron	Bright green
Ba	Barium	Pale/Apple green
Ca	Calcium	Brick red
Cs	Caesium	Blue-Violet
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(violet)
Li	Lithium	Pink-Red
Mn (II)	Manganese (II)	Yellowish green
Mg	Magnesium	No colour
Mo	Molybdenum	Yellowish green
Na	Sodium	Intense yellow
P	Phosphorus	Pale bluish green
Pb	Lead	Blue
Rb	Rubidium	Red-violet
Sb	Antimony	Pale green
Se	Selenium	Azure blue
Sr	Strontium	Red
Te	Tellurium	Pale green
Tl	Thallium	Pure green
Zn	Zinc	Bluish green