Types and application of chemical dyes

1. CHEMISTRY SEMINAR ON
CHEMISTRY IN DAILY LIFE
(DYES)
AISHWARYA. B

2. DYES ARE COLOURED ORGANIC
COMPOUNDS HAVING THE
PROPERTY OF FIRMLY IMPARTING
COLOUR TO OTHER SUBSTANCES
SUCH AS TEXTILE FIBRES, WOOL,
SILK, LEATHER, PAPER, INK, TOYS,
HAIR, FOODSTUFF ETC.

3. NATURAL DYES
The dyes that are originally obtained from plants and animals and
are used to colour the cloth are called natural dyes.
For eg, Tyrian purple was extracted from sea snail by the romans
to colour the clothes of the nobles. The red dye Carmine used to
be extracted from the cochineal insects

4. SYNTHETIC DYES
• The dyes that are produced
industrially from organic
compounds are called
synthetic dyes. Sir William
Henry Perkin had
accidentally synthesized the
purple dye mauveine while
trying to make quinine.

5. REQUIREMENTS OF A DYE
1. Must have a suitable colour
2. Must be capable of fixing itself permanently to the material to
be dyed
3. When fixed to the material it must retain its colour even in
prolonged sunlight and other atmospheric conditions and
while washing and drying. This property is called fastness of a
dye.
4. It must be faster to dye when compared to normal dyes
5. Sufficient solubility of a dye in water or aqueous solution
should be maintained.

6. THEORIES OF COLOUR AND
CONSTITUTION1. Witt’s Theory
Otto Witt had said that the atructures of dye are essentially made up
of two parts- chromophore and auxochrome:
Chromophore is a group that produces colour. The presence of
atleast one chromophore is essential to produce colour. The
compound containing at least one chromophore is called
Chromogen. Most of the chromogens have unsaturations in them.
The greater the intensity of the chromophore in chromogen, greater
will be the intensity of colour.
Auxochrome is a group which does not produce colour on its own
but is able to jntensity only in the presence of a chromophore when
present together. The presence of auxochome is necessary for a
chromogen to function as a dye.

7. Valence Bond Theory
Chromophores are the groups in which π electron get excited from lower levels to
higher levels by absorption of radiation quanta in the visible regions. This produces
vcolour in those chromogens
Auxochromes augment resonance in the chromogens by allowing interaction of
their lone pair with the π electrons of the chromogens. This results in bathochromic
effect or red shift. Shift absorption from higher to lower wavelength are called blue
shift or hypsochromic shift.

8. STRUCTURES AND APPLICATIONS
OF CERTAIN DYESMARTIUS YELLOW
Martiys yellow is a nitro dye containing 2,4-dinitro-1-
napthol.Matius yellow is a direct dye applied directly to
the fabric from aqueous solution. Some of its uses are:
1. Used to dye silk and wool.
2. It can also be used to dye the synthetic fibres
nylons.
3. It is used as a yellow biological stain in microscopy.
4. It is used as a chemical indicator.

9. Indigo
Indigo is a vat dye. A vat dye is an jnsoluble dye
which is first reduced to a colourless soluble form in
large vats, then applied to the fabric, and then finally
oxidised back to the insoluble coloured form by air
or an oxidants.
1) Indigo is used to dye cotton, which is mainly for
the production of denim cloth for blue jeans.
2) It can also be used to dye wool and silk.
3) Indigo carmine, a derivative of indigo, is used as
a food colourant.

10. Alizarin
Alizarin is an anthraquinone dye. Alizarin is 1,2-
dihydroxyanthraquinone.A mordant dye is a dye which does not
attach itself to the fabrics but require a mordant to act as
binding agent between it and the fabric. Some of the uses of
alizarin below:
1) Alizarin is used to dye cotton and wool, and the colour
developed depends upon the mordant metal ion used.
2) It is used as a biological stain in medicinal studies involving
calcium as well as calcium compound in bones and other
tissues can be staimed red or a light purple using alizarin
3) It is used in geology as a stain to indicate mineral containing
calcium
4) It has been in use a red pigment in paintings aantiquity.
5) It is used in making printing inks
6) Alizarin and its derivatives are used as spot test reagent in
chemical analysis.

11. THANK YOU✌