chemistry investigatory

project
topic: dyeing of fabrics

mehardip kaur
class 12A
roll no:

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 Acknowledgement

I would like to express a deep sense of thanks and gratitude to my

chemistry teacher Mrs. Geetu Madan for guiding me immensely

through the course of my project. Their constructive advice and

constant motivation have been responsible for the successful

completion of my project.

My sincere thanks to my parents for their motivation and support.

I must thank my classmates for their timely help and support for

compilation of this project.

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 Introduction of dyes:
Dyes are coloured substances which
can adhere to the surface of materials
and are used to give colour to paper,
food-stu s and various textiles such
as cotton, wool, synthetic bres, silk
etc. For example, alizarin, indigo,
congo red, etc. Chemically, a dye
contains:
(i) Some group (such as azo, indigoid,
triphenylmethyl, anthraquinone, etc.)
which is responsible for the colour of the
dye.
(ii) Some group (such as -NH2 - SO3H,
-COOH, etc.) which makes the dye
stick to the fabric by formation of
some salt.
The dyed fabrics appear to be
coloured because a particular dye
absorbs radiations of some speci c
wavelengths from the visible region of
electromagnetic radiations which fall on
C14H802 — anthraquinone
its surface. The remaining radiations
(complementary colours) of light are
re ected. The colour which we observe is due to this re ected
light. For example,
• if a dye absorbs the light in the wavelength region
corresponding to red then it would appear green, which is the
complementary colour of red.
• Similarly, if a dye absorbs blue colour, it would appear orange.

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 Characteristics of a dye:

1. must have a suitable color

2. must be capable of being xed to the material
3. when xed it must be fast to detergents, soaps, water, dry-
cleaning solvents, light and dilute acids.

Types of dyes:

The dyes are classi ed by dye manufacturers for marketing into

the following types:
1. Acid dyes: These are azo dyes and are characterised by the
presence of acidic groups. The presence of acidic group makes the
dyes more soluble and serves as the reactive points for xing
the dye to the bre. They are chie y used for dyeing wool, silk
and nylon.

example, Orange I and Orange II.

2. Basic dyes: These dyes contain

organic basic groups such as NH2 or NR2.

In acidic solutions, these form water
soluble cations and use the anionic
site on the fabric to get themselves
attached.
These are used for dyeing wool,
silk and nylon.
examples: aniline yellow, butter
yellow.
C12H11N3-aneline yellow

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 3. Direct dyes: These are also azo dyes and are used to dye the
fabrics directly by placing in aqueous solution of the dye. These
dyes attach to the fabrics by means of hydrogen bonding.
4. Disperse dyes: These dyes are applied in the form of a
dispersion of minute particles of the dye in a soap solution in
the presence of phenol or
benzoic acid. These dyes are
used to dye rayons, dacron,
nylon, polyesters etc.
example: celliton fast pink B

and celliton fast blue B.

5. Fibre reactive dyes: These dyes are linked to the bre by -OH
or by
-NH, group present on the bre. These dyes induce fast colour
on bres which is retained for a longer time. These dyes are
used for dyeing cotton, wool and silk.
6. Insoluble dyes: These dyes are directly synthesised on the
bre. The fabric to be coloured is soaked in an alkaline solution
of phenol and then treated with a solution of diazotised amine to
produce azo dye. The colour induced by such dyes is not fast.
These dyes are used for dyeing of cotton,
silk, polyester nylon, etc.
example: nitroaniline red.
7. Vat dyes: These dyes are water-insoluble and before dyeing
these are reduced to colourless compounds in wooden vats by
alkaline reducing agent. The re is then soaked in the solution of
the dye. Fibre is then exposed to air or an oxidizing agent. By

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doing so the colourless compound gets reoxidised to coloured
dye on the fabric. example: indigo.
8. Mordant dyes: These dyes are applied after treating the fabric
with precipitates of certain substances (mordant material) which
then combines with the dye to form a coloured complex called
lake. Some of the mordants are salts of aluminium, iron and
tannic acids. Depending on the mordant used, the same
mordant dye can give di erent colour and shades. Mordant
dyes are used for dyeing of wool, silk and cotton.
example:
1. alizarin gives red colour with aluminium

2. black violet with iron mordant

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 Experiment-1

Aim: To dye wool and cotton clothes with malachite green

Requirements: 500 ml beakers, tripod stand, wire gauze, glass
rod, spatula, wool cloth and cotton cloth. Sodium carbonate,
tannic acid, tartaremetic and malachite green dye (Chemical
formula: C6H5C(C6H4N(CH3)2)2]CI ; Common Name:
Triarylmethane dye)

Procedure:

1. Preparation of sodium carbonate solution: take about 0.5 g of

solid sodium carbonate and dissolve it in 250 ml of water.
2. Preparation of tartaremetic solution: Take about 0.2 g of
tartaremetic and dissolve it in 100 ml of water by stirring with
the help of glass rod.

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 3. Preparation of tannic acid solution: Take 100 ml of water in a
beaker and add about 1.0 g of tannic acid to it. Heat the
solution. On heating a clear solution of tannic acid is obtained.
4. Preparation of dye solution: Take about 0.1 g of malachite
green dye and add to it 400 ml of water. On warming a clear
solution of the dye results.
5. Dyeing of wool: Take about 200 ml of dye
solution and dip in it the woollen cloth to be
dyed. Boil the solution for about 2 minutes.
After that remove the cloth and wash it with
hot water
3-4 times, squeeze and keep it for drying.
6. Dyeing of cotton: Cotton does not absorb
malachite green readily, therefore it requires
the use of a mordant. For dyeing a cotton
cloth dip it in sodium carbonate solution for
about 10 minutes and then rinse with water.
Then put the cloth in hot tannic acid
solution for about 5 minutes.
Now take out the cloth from tannic acid
solution and keep it in tartaremetic solution
for about 5 minutes. Remove the cloth and
squeeze it with spatula to remove most of
the solution. Now place the cloth in boiling
solution of the dye for about 2 minutes.
Remove and wash the dyed cloth thoroughly
with water, squeeze and keep it for drying.
7. Dyeing of cotton directly: Take another piece of cotton cloth
and put it directly into boiling solution of the dye. Keep it dipped
for about 2 minutes. Remove the cloth, wash with water,
squeeze and keep it for drying. Compare the colour of this cloth
with that of dyed by using mordant.

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OBSERVATIONS:
1. The colour of wool cloth dyed directly by dipping in hot
solution of malachite green dye is fast.
2. The colour of cotton cloth dyed directly (without using
mordant) by dipping in hot solution of malachite green is not
fast to washing and is of low intensity.
3. The colour of cotton cloth dyed indirectly by using mordant
and then by dipping in hot solution of malachite green is fast
to washing and is of high intensity.

PRECAUTIONS:

1. While dyeing cotton directly, let the cotton cloth be present

in the dye for more than or equal to 2 minutes but not less.
2. Using of solutions such as tartaremetic solution, tannic acid
solution must be eminent.
3. Usage of gloves is preferable to ensure tidiness.

Conclusion

DYE FABRIC RESULT

MALACHITE GREEN WOOL FAST

MALACHITE GREEN COTTON NOT FAST TO WASHING

LOW INTENSITY

SODIUM CARBONATE COTTON FAST TO WASHING

SOLN+ TARAREMETIC HIGH INTENSITY
SOLN + TANNIC SOLN
+ MALACHITE GREEN

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