CONTENTS

Introduction

Objective

Requirements

Procedure

Conclusion

Bibliography
 INTRODUCTION
 Dyes are colored substances which can adhere to the
surface of materials and are used to give color to paper,
food-stu s, and various textiles such as cotton, wool,
synthetic fibers, silk etc. For example, alizarin, indigo,
Congo red, etc. Chemically, a dye contains:
 Some group (such as azo, indigoid, triphenylmethyl,
anthraquinone, etc.) which is responsible for the color of
the dye.
 Some groups (such as –NH2, -SO3H, -COOH, etc) which
makes the dye stick to the fabric by formation of some
salt.
 Dyeing is the process of adding color to textile products
like fibers, yarn and fabrics. The temperature and time
controlling are two key factors in dyeing.
 The primary source of dye, historically has been nature,
with the dyes being extracted from plants and animals.
Since the 18th century, humans produced artificial dyes
to achieve a broader range of colors and to render the
dyes more stable to resist washing and general use.
 The dyed fabrics appear to be colored because a
particular dye absorbs radiations of some specific
wavelengths from the visible region of electromagnetic
radiations which fall
 TYPES OF DYES
The dyes are classified by dye manufacturers for marketing
into the following types:
1. Acid dyes: These are azo dyes and are characterized by the
presence of acidic groups. The presence of soluble and serves
as the reactive points for fixing the dye to the fibre. They are
chiefly used for dyeing wool, silk and nylon. For example,
Orange I and Orange II.
2. Basic dyes: These dyes contain NH2 or NR2. In acidic
solutions, these form water soluble cations and use the
anionic sites on the fabric to
get used for dyeing wool, silk and nylon. For example, aniline
yellow, butter yellow.
3. Direct dyes: These are also azo dyes and are used to dye
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
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. For example, celli
ton fast pink B and Colliton fast blue B.
5. Fibre ractive dyes: These dyes are linked to the fibre by –
OH or –NH2 group present on the fibre. These dyes induce fast
color on fabrics which is retained for a longer time. These dyes
are used for dyeing cotton, wool and silk.
6. Insoluble dyes: These dyes are directly synthesized on the
fibre. The fabric to be colored is soaked in an alkaline solution
of phenol and then treated with a solution of diazotized amine
to produce azo dye. The color induced by such dyes is not so
fast. These dyes are used for dyeing of cotton, silk, polyester
nylon, etc. For example, nitroaniline red.
7. Vat dyes: These dyes are water-insoluble and before dyeing
these are reduced to colorless compounds in wooden vats by
alkaline reducing agents. The fibre is then soaked in the
solution of the dye. Fibre is then exposed to air or an oxidizing
agent. By doing so the colorless compound gets reoxidized to
colored dye on the fabric. For 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 colored
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 colors
and shades. For example, alizarin gives red color with
aluminium and black violet with iron mordant. Mordant dyes
are used for dyeing of wool, silk and cotton.
OBJECTIVE
To dye wool and cotton with malachite green.

REQUIREMENTS
500 ml beakers, tripod stand, wire gauze, glass rod,
spatula, wool cloth and cotton cloth.
Chemicals required: Sodium carbonate, tannic acid,
tartaremetic acid, and malachite green 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 tartar emetic solution: Take about 0.2 g of
tartar emetic and dissolve it in 100 ml of water by stirring
with the help of glass rod.
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 4oo 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 it in the woolen 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 tartar emetic 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 pit 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 color of this cloth with that dyed by using
mordant.
 OBSERVATIONS

1. The color of wool cloth dyed directly by dipping in

hot solution of malachite green dye is fast.

2. The color of cotton dyed cloth directly (without

using mordant) by dipping in hot solution of
malachite green is not so fast to washing and is of
low intensity.

3. The color 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.
 BIBLIOGRAPHY

Comprehensive practical chemistry (class 12)

www.wikipedia.org/wiki/Dyeing

www.scribd.com