Identification of cotton fiber

1. Burn Test: The burn test is a quick way to determine the cotton fiber. A few threads from the fiber is moved slowly to the flame of the burner and then into it. Where it is watched carefully. Then the sample is removed from the flame still watching it. The fiber sample is evaluated considering the following point.
a.       Ability to ignition.
b.      Art of burn.
c.       Smell.
d.      Combustion residue.
When cotton ignited it will not shrink from the flame will burn with a yellow flame. It continues to burn when the flame is removed and smell like burning paper. There is a little grey ash residue after combustion.
2. Chemical test:
i. Treatment with H2SO4: With concentrated H2SO4 the cotton fiber will be destroyed, i.e. the cellulose components will be dissolved.
ii. Iodine potassium iodide test: The iodine potassium iodide solution is prepared by dissolving 20gm iodine in 100ml solution of potassium iodine. The samples are treated some seconds with this solution followed by rinsing with water unmercerized cotton will not be colored, where as the mercerized cotton remain longer time dark blue to blue colored.