Page 208 - ICSE Chemistry 8

Lampblack or Carbon Black or Soot

Lampblack contains 98–99% carbon. It is prepared by burning hydrocarbons
like oil, wax, kerosene oil, paraffi n, naphthalene or petrol in a limited supply of
air. These substances burn with a smoky fl ame which contains a large amount
of free carbon. When this smoke is allowed to cool on a surface, carbon se les
en
down as a fi ne black powder. The deposited fi ne black powder or soot is then
scraped off the surface and collected. In India, it is used as kajal.

Uses of Lampblack Fig. 9.9: Kajal

• It is used as a pigment in making printer’s ink, carbon paper, black
paint and shoe polish.
• It is used in hardening of rubber tyres.

• It is used in the manufacturing of gun powder.

Take a Break!

Match the columns.

Column A Column B
1. Hard coke (a) Black and porous substance used in household furnaces

2. Gas carbon (b) Manufacturing of metallic carbides

3. Lampblack (c) Light, lustrous substance used in industrial furnaces
4. So coke (d) Prepared by burning of hydrocarbons

(e) Greyish substance obtained by destruc ve dis lla on
5. Coke
of coal

Let’s perform Ac vity 9.7 to observe the process of prepara on of kajal from vegetable oil.

Activity 9.7

Aim: To prepare kajal from vegetable oil
Materials required: Some mustard oil or ghee, an earthen lamp, a
co on wick, a metal plate

Procedure
black powder
• Take some mustard oil or ghee in an earthen lamp (diya) and (soot)
put a co on wick in it.
• Light the co on wick.

• Now hold a metal plate over the fl ame as shown in the fi gure.
Observa on: You will observe that black powder (soot) deposits on the surface of the plate.

Conclusion: The black powder formed is called kajal.

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