Textiles, Bleaching and Dyeing
An Introduction
Textiles
• Ancient craft using natural resources (wool,
cotton, flax) for making fabric for clothing,
shelter, bedding, floor covering, ...
• Mechanical aspects: picking, cleaning,
carding, spinning, weaving and making final
product.
• During the Industrial Revolution, the textile
industry rapidly expanded and advanced
technologically.
Industrial Revolution
• New inventions were assisted by the patent
process, availability of investors, preventing
knowledge to leave Britain.
• Advances in power: manual, water, steam
engines.
• Growing sources of natural resources and
markets (colonies).
• Improving transportation infrastructure.
Textiles: Bleaching
• Bleaching fabric whitens it.
• Pre-IR: wash in soap, boil fabric in strong base
(lye soda ash; also NaOH), expose to sunlight.
• Transition to Palaeotechnic: soak in weak acid
(sulphuric and hydrochloric), and then base
(lime, alkali).
• Palaeotechnic: use of chlorine as bleach
(Berthollet and Scheele, France , 1785)
How Does Bleach Work?
• Bleach oxidizes compounds (stains, dye,
germs) by breaking chemical bonds and
inserting oxygen or by converting C=C and/or
C=O double bonds to single bonds.
Chemistry
• 1785
H2SO4 + 2NaCl  Na2SO4 + 2HCl
Vitriol + common salt 
2HCl + MnO2  Cl2 + MnO + H2O
muriatic acid + black calx of Mn 
• H2O + Cl2 (aq)  2H+(aq) + Cl-(aq) + OCl(aq)
Water + chlorine  hydrogen and chloride ions
and HYPOCHLORITE ion
Textiles: Dyeing
• Dyes give color to fabric.
• The first dyes were from minerals or extracted
from plants and animals. Most of the latter
were organic molecules (primarily C and H).
• Indigo was one of the earliest organic dyes.
Chemical Questions
• As advances in textile production and
bleaching were made, interest in fabric dyes
increased: studying its chemical composition,
improving extraction methods, modifying
chemical composition to produce different
dyes, discovering ways to make the dyes more
colorfast , minimizing toxicity...There was a
rich chemistry involved in these investigations.
From Natural Dyes to Synthetic Dyes
• The next logical step was to make dyes from
chemicals in the lab or manufactory.
• The first dye was synthesized by Perkins (an 18
year old lab assistant in London) in 1856:
Tyrian purple, mauve or maureine.
• This grew out of the products of the coal tar
industry, one of which was aniline.
• These dyes are organic compounds.
Synthesis of the Dye called Mauve
• REACTANTS: C6H7N + K2Cr2O7 + C7H9N + H2SO4
aniline + potassium dichromate + p-toluidine +
sulfuric acid
• PRODUCTS: a complex mixture of at least four
methyl derivatives (C24 to C28) with a 7-amino-5phenyl-3-(phenylamino)phenazin-5-ium core.
http://www3.interscience.wiley.com/journal/121
359283/abstract?CRETRY=1&SRETRY=0
• Products first verified in 1994 with more work in
2007
Mauveine
Chemical Structures
Aniline and Toluidine
One Structure of Mauveine
Chromophores
• The C =C bonds in the dye absorb light in the
ultra-violet (λ < 200 nm) and visible (λ = 200700 nm) region of the light spectrum causing
the dye molecule to go from a ground state to
an excited state. When the molecule returns
to the ground state, visible light (λ = 450 nm;
purple; ) is emitted and observed.
• These molecules are called chromophores
(chrom = color).
Visible Light Spectrum
• http://images.google.co.uk/images?q=visible+
spectrum&ie=UTF-8&oe=utf8&rls=org.mozilla:enUS:official&client=firefoxa&um=1&sa=X&oi=image_result_group&resn
um=4&ct=title
• 400 nm = violet; 500 nm = green; 575 nm =
yellow; 700 nm = red
Dyes – Fabric Bond
• Dyes must adhere to the fabric. There are two
mechanisms
– The formation of chemical bonds between the
fabric and dye.
– The use of a third compound (called a mordant
like alum) to form an insoluble compound with
the dye. This product then adheres to the fabric.
References
• http://potency.berkeley.edu/chempages/ANILI
NE.html
• http://www.chemsynthesis.com/base/chemic
al-structure-3482.html
• http://www.rsc.org/Publishing/ChemScience/
Volume/2007/06/mysteries_mauve.asp