In cigarette lighters, the hottest part of the flame is the tip of the inner blue cone. This area is where the combustion process is most efficient, resulting in the highest temperature. The blue color indicates complete combustion, which means the fuel is burning efficiently with enough oxygen.
The outer flame, which is usually yellow or orange, is cooler because it is not burning as efficiently. This part of the flame has less oxygen and more unburned fuel particles, which results in a lower temperature.
Understanding the different parts of the flame can be useful for various applications, such as lighting cigarettes or other materials that require a consistent and high-temperature flame.