What Colors Should You Expect from the Flame Test?

What Colors Should You Expect from the Flame Test?

 From left to right, these are flame test colors of cesium chloride, boric acid, and calcium chloride. (c) Philip Evans / Getty Images

The flame test is a fun and useful analytical technique to help you identify the chemical composition of a sample based on the way it changes the color of a flame. However, interpreting your results can be tricky if you don't have a reference. There are many shades of green, red, and blue, usually described with color names you wouldn't even find on a crayon box! So, here are some sample photographs of flame test colors. Keep in mind, your results may vary depending on your technique and the purity of your sample. It's a good place to start, though.

Flame Test Colors Depend on Technique

 It's common to view a flame test result through a filter. Westend61 / Getty Images

Before I get into the photos, you need to remember the color you should expect will depend on the fuel you are using for your flame and whether or not you're viewing the result with the naked eye or through a filter. It's a good idea to describe your result in as much detail as you can. You might want to take pictures with your phone to compare results from other samples.

Sodium - Yellow Flame Test

 Sodium salts burn yellow in the flame test. Trish Gant / Getty Images

Most fuels contain sodium (e.g., candles and wood), so you're familiar with the yellow color this metal adds to a flame. The color is muted when sodium salts are placed in a blue flame, like a Bunsen burner or alcohol lamp. Be aware, sodium yellow overwhelms other colors. If your sample has any sodium contamination, the color you observe may include an unexpected contribution from yellow!

Iron can also produce a golden flame (although sometimes orange).

Potassium - Purple in a Flame Test

 Potassium and its compounds burn violet or purple in a flame test. Dorling Kindersley, Getty Images

Potassium salts produce a characteristic purple or violet color in a flame. Assuming your burner flame is blue, it may be difficult to see a big color change. Also, the color may be paler than you expect (more lilac).

Cesium - Purple-Blue in a Flame Test

 Cesium turns a flame violet in a flame test. (c) Philip Evans / Getty Images

The flame test color you're most likely to confuse with potassium is cesium. Its salts color a flame violet or blue-purple. The good news here is most school labs don't have cesium compounds. Side-by-side, potassium tends to be paler and have a slight pink tint. It may not be possible to tell the two metals apart using only this test.

Strontium - Red Flame Test

 Strontium compounds turn a flame red. Dorling Kindersley / Getty Images

The flame test color for strontium is the red of emergency flares and red fireworks. It's a deep crimson to brick red.

Barium - Green Flame Test

 Barium salts produce a yellow-green flame. stay hungry for more, Getty Images

Barium salts produce a green flame in the flame test. It's usually described as a yellow-green, apple green, or lime green color. The identity of the anion and the concentration of the chemical matter. Sometimes barium produces a yellow flame without noticeable green.

Manganese(II) and molybdenum may also yield yellow-green flames.

Copper(II) - Green Flame Test

 This is the green flame test result from a copper(II) salt. Trish Gant / Getty Images

Copper colors a flame green, blue, or both depending on its oxidation state. Copper(II) produces a green flame. The compound it's mostly likely to be confused with is boron, which produces a similar green.

Copper(I) - Blue Flame Test

 This is a blue-green flame test result from a copper compound. Dorling Kindersley / Getty Images

Copper(I) salts produce a blue flame test result. If there is some copper(II) present, you'll get blue-green.

Boron - Green Flame Test

 This fire vortex is colored green using a boron salt. Anne Helmenstine

Boron colors a flame bright green. It's a common sample for a school lab because borax is readily available in many places.

Lithium - Hot Pink Flame Test

 Lithium salts turn a flame hot pink to magenta. stay hungry for more, Getty Images

Lithium yields a flame test somewhere between red and purple. It's possible to get a vivid hot pink color, although more muted colors are also possible. It's less red than strontium. It's possible to confuse the result with potassium.

Another element which may produce a similar color is rubidium. For that matter, so can radium, but it's not commonly encountered.

Calcium - Orange Flame Test

 Calcium carbonate produces an orange flame test color. Trish Gant / Getty Images

Calcium salts produce an orange flame. However, the color may be muted, so it can be hard to distinguish between the yellow of sodium or gold of iron. The usual lab sample is calcium carbonate. If the specimen is not contaminated with sodium, you should get a nice orange color.

Blue Flame Test Results

 A blue flame test might not tell you which element is present, but at least you know which ones to exclude. Dorling Kindersley / Getty Images

Blue is tricky, because it's the usual color of a methanol or burner flame. Other elements that can impart a blue color to a flame test are zinc, selenium, antimony, arsenic, lead, and indium. Plus, there are a host of elements that don't change the color of a flame. If the flame test result is blue, you won't get much information, except you can exclud