12 Difference Between Luminous And Non-Luminous Flame With Examples

The Bunsen burner has a controllable air supply and a constant gas jet, therefore when the air supply is reduced; a highly visible, yellow/orange ‘safe flame’ is produced. For heating work, the air inlet is opened and the burner produces a much hotter blue flame. Therefore, the two flames produced by a Bunsen burner can be categorized as:

• Luminous Flame
• Non-luminous flame

Luminous Flame

Luminous flame is a type flame produced by a Bunsen burner when the air-hole (part of the Bunsen burner) is opened. The flame is generally yellow in color, large and wavy. It is fully visible since it produces a bright glowing flame.

When the air hole of the Bunsen burner is closed, very little air enters the barrel of the burner, thus the gas only mixes with surrounding air at the point of combustion at the top of the burner. In this case, the flame will be yellow, large, unsteady, bright and sooty due to incomplete combustion.

Luminous flames are not used in experiments (not best for laboratory operations) because it is wavy and sooty in nature. Examples of luminous flames include burning wood, candles, Olympic cauldron etc.

Luminous flame has three main regions (parts):

• The top yellow region where there is incomplete combustion/burning.
• The region of unburnt gas below the yellow region where the gas does not burn.
• Blue region on the sides of region of unburnt gas where there is complete burning.

Facts About Luminous Flame

1. Luminous flames are bright yellow in color.
2. Luminous flames are sooty (produce soot)
3. In a Bunsen burner, luminous flame is formed when the air-hole is completely closed.
4. Luminous flames are not very hot (produce less heat).
5. Luminous flame produces more light.
6. Flames are not steady (do not burn steadily).
7. Luminous flames do not burn more efficiently. Luminous flames do not get enough oxygen to turn all the carbon that is being burnt into carbon dioxide.
8. Luminous flames are wavy and brightly visible
9. Luminous flames have limited access to oxygen.
10. Luminous flames are not used in experiments (not best for laboratory operations) because it is wavy and sooty in nature.
11. Examples of luminous flamesinclude burning wood, candles, Olympic cauldron etc.

Non-luminous Flame

A non-luminous flame is the type of flame produced by the Bunsen burner when the air-hole is closed. The flame is generally blue in color, small, steady and cannot be seen from far. It usually burns with a roaring sound.

When the air-hole of the Bunsen burner is fully opened, sufficient air enters the Bunsen burner barrel and mixes well with the coal gas, hence, the burning of the gas is much quicker and complete. The flame is smaller and hotter. Due to the absence of white-hot carbon, no light appears.

Due to unlimited supply of air, there is usually complete combustion of carbon and thus non-luminous flames are hotter and do not produce soot. For this reason, they are most preferably used in experiments (laboratory operations). Examples of non-luminous flames include flames of a Bunsen burner when the air-hole is closed, acetylene torches etc.

Non-luminous flame has four main regions (parts):

• The top colorless region.
• Blue region just below where there is complete burning. It is the hottest region.
• Green region surrounded by the blue region where there is complete burning.
• The region of unburnt gas at the innermost surrounded by green and blue regions. No burning takes place here.

Facts About Non-luminous Flame

1. Non-luminous flame is light blue in color.
2. Non-luminous flames are not sooty (does not produce soot).
3. In a Bunsen burner, non-luminous flames are formed when the air-hole is opened.
4. Non-luminous flames are very hot (Produce more heat).
5. Non-luminous flames produce little light.
6. Flames are steady.
7. Non-luminous flames burn more efficiently because they are able to combine all their carbon with oxygen.
8. Non-luminous flames are hardly visible and less wavy.
9. Non-luminous flames have unlimited access to oxygen.
10. Non-Luminous flames are most preferably used in experiments (laboratory operations) because they are hot, not sooty, and less wavy and hence easy to control.
11. Examples of non-luminous flamesinclude flames of a Bunsen burner when the air-hole is closed, acetylene torches etc.

Also Read: Difference Between Phylogenetic Tree And Cladogram

Difference Between Luminous And Non-Luminous Flame In Tabular Form

Uses of Flames

Flames are used for different purposes. Some uses of the flames include the following:

• Production of heat for heating substances in the laboratory: In this case, a non-luminous flame, which produces much heat, is used. However, for reactions that require little heat, a luminous flame, which is not very hot, can be used.
• Flame tests for elements: In chemical analysis of some elements, a flame test is one of the preliminary tests normally used to identify an element. When some elements are strongly heated, they produce characteristic flame colours that distinguish them from one another. A non-luminous flame is often used.
• Production of light: Flames produce light that can be used to light a dark room. Therefore, an experiment that involves heating can even be conducted in the dark. The same flame is used to give heat as well as light. Here, a luminous flame is used. Examples of heat sources, which produce flames that may be used for lighting, are hurricane lamp, tin lamp, spirit lamp and candle.
• Cooking: Since it gives a hot flame and produces no soot, a non-luminous flame can be used for cooking food. Gas cookers, gas stoves and kerosene stoves usually produce such flames.
• Welding: A non-luminous flame is suitable for welding because it is very hot. In most welding operations, an oxyacetylene gas, a mixture of oxygen and ethyne, is used. When burned, the gas produces a flame hot enough to cut or melt the metal.