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Xavier University Ateneo de Cagayan Corrales Avenue, Cagayan de Oro City Cyclic Intermediates and Dyes Submitted to: Engr. Edwin Richard R. Ortiz ChE 511 Instructor Submitted by: Ilea A. Verano BS ChE 5 August 16, 2010
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Page 1: Cyclic Intermediates and Dyes

Xavier University – Ateneo de Cagayan Corrales Avenue, Cagayan de Oro City

Cyclic Intermediates and Dyes

Submitted to: Engr. Edwin Richard R. Ortiz

ChE 511 Instructor

Submitted by: Ilea A. Verano

BS ChE 5

August 16, 2010

Page 2: Cyclic Intermediates and Dyes

REPORT OUTLINE: Cyclic Intermediates and Dyes

I. Dye Intermediates

II. Intermediate Classification

a. Inorganic Materials

b. Primary Intermediates

c. Dye Intermediates

III. Introduction to Dyes

IV. Classification System for Dyes

a. Classification by Chemical Class

b. Classification by Usage or Application

V. Nomenclature of Dyes

a. Commercial Trade Name

b. Colour Index

VI. Equipment and Manufacture

a. Reaction

b. Product Isolation

c. Product drying, grinding, and/or finishing

d. Waste Characteristics

Page 3: Cyclic Intermediates and Dyes

I. DYE INTERMEDIATES

The precursors of dyes are called dye intermediates. They are obtained from

simple raw materials, such as benzene and naphthalene, by a variety of chemical

reactions. Usually, the raw materials are cyclic aromatic compounds, but acyclic

precursors are used to synthesize heterocyclic intermediates. The intermediates

are derived from two principal sources, coal tar and petroleum.

II. SOURCES OF RAW MATERIALS

Coal tar results from the pyrolysis of coal and is obtained chiefly as a by-product in

the manufacture of coke for the steel industry. Products recovered from the

fractional distillation of coal tar have been the traditional organic raw material for

the dye industry. Among the most important are benzene, toluene, xylene

naphthalene, anthracene, acenaphthene, pyrene, pyridine, carbazole, phenol, and

cresol.

The petroleum industry is now the principal supplier of benzene, toluene, the

xylenes, and naphthalene. Petroleum displaced coal tar as the primary source for

these aromatic compounds after World War II because it was relatively cheap and

abundantly available. However, the re-emergence of king coal is predicted for the

twenty-first century, when oil supplies are expected to dwindle and the cost of

producing chemicals from coal (including new processes based on synthesis gas)

will gradually become more competitive.

Page 4: Cyclic Intermediates and Dyes

III. INTERMEDIATES CLASSIFICATION

Intermediates may be conveniently divided into primary intermediates (primaries)

and dye intermediates. Large amounts of inorganic materials are consumed in both

intermediates and dyes manufacture.

a. Inorganic Materials

These include acids (sulfuric, nitric, hydrochloric, and phosphoric), bases (caustic

soda, caustic potash, soda ash, sodium carbonate, ammonia, and lime), salts

(sodium chloride, sodium nitrite, and sodium sulfide) and other substances such as

chlorine, bromine, phosphorus chlorides, and sulfur chlorides. The important point

is that there is a significant usage of at least one inorganic material in all

processes, and the overall tonnage used by, and therefore the cost to, the dye

industry is high.

b. Primary Intermediates

Primary intermediates are characterized by one or more of the following

descriptions, which associate them with raw materials rather than with

intermediates.

1. Manufactured in a dedicated plant, i.e., one devoted to a single product or at

most two or three closely related products.

2. At least 1000 t/yr capacity from a single plant and may be up to 100,000 t/yr, e.g.,

aniline.

Page 5: Cyclic Intermediates and Dyes

3. Manufacturing process and/or operation is continuous or semicontinuous, i.e., at

least one stage is in a continuous, as distinct from batch, mode.

4. A primary intermediate has established usage in basic industries such as rubber,

polymers, or agrochemicals in addition to dyes.

c. Dye Intermediates

Dye intermediates are defined as those precursors to colorants that are

manufactured within the dyes industry, and they are nearly always colorless.

Colored precursors are conveniently termed color bases. As distinct from primaries

they are only rarely manufactured in single-product units because of the

comparatively low tonnages required. Fluorescent brightening agents (FBAs) are

neither intermediates nor true colorants.

Intermediates vary in complexity, usually related to the number of chemical and

operational stages in their manufacture, and therefore cost. Prices may be classed

as cheap (less than $1500/t, as with primaries), average ($1500 to $5000/t) or

expensive (more than $5000/t).

IV. INTRODUCTION TO DYES

Frequently the color of a product is the reason for its sale. For this reason, it is

dyes are important for manufacturers to control and manipulate the color or hue of

their final product. Dyes add value to products far beyond their cost.

Page 6: Cyclic Intermediates and Dyes

Dyes are colored, ionizing and aromatic organic compounds which show an affinity

towards the substrate (textile, leather, etc.) to which it is being applied.

The preparation and application of dyestuffs is one of the oldest forms of human

activities. Evidences of which were found by excavation at archeological sites

where ancient fabrics were unearthed. There is also mention of it in the Bible and

other works of classical antiquity. It was in 2600 BC when earliest written records

of the use of dyestuffs were found in China.

Perhaps one of the real breakthroughs in the history of dyes came in 1856 when a

teenager who was experimenting at his makeshift laboratory in home made a

certain discovery that acted as a sort of launching pad for the modern chemicals

industry.

William Perkin an 18-year-old student was working on chemical synthesis of

natural products. William Perkin chanced upon his now famous 'Aniline Mauve' dye

while he was attempting to synthesize quinine, the only cure for malaria. Perkin

named his color Mauveine, after the French name of non-fast color which was

made of natural dyes. So "Mauve" (a basic dye) was the first synthetic dye stuff.

Mauve was a derivative of coal tar. It was the first mass-produced dye, that was

commercially available and the idea was born that a color could be made in the

factory.

Page 7: Cyclic Intermediates and Dyes

For dyes to be effective, they must be colored and must impart its color to

something else (formally called a substrate) on a reasonably permanent basis. A

dye consists of a color-producing structure, the chromogen (electron acceptor) and

a part to regulate the solubility and dyeing properties, the auxochrome (electron

donor). The chromogen is an aromatic body containing a color-giving group

commonly called the chromophore. Chromophore groups cause color by altering

absorption bands in the visible spectrum.

Some of the common chromophores are:

1. The nitroso group

2. The nitro group

3. The azo group

4. The ethylene group

5. The carbonyl group

6. The carbon-nitrogen groups

7. The carbon-sulfur groups

These groups add color to aromatic bodies by causing displacement of, or an

appearance of, absorbent bands in the visible spectrum. The chromophore groups

are the basis of one method of classifying dyes.

Some molecules lose their colors when the chromophore groups are saturated.

The auxochromes, the part of the dye which causes it to adhere to the material

Page 8: Cyclic Intermediates and Dyes

which it colors usually are: -NH2, -OH, -NR2, -COOH and SO3H. These

auxochromes are salt-forming which aids the solubility of the dye in acidic and

basic medium. Auxochromes also aid to intensify the color of dyes.

V. CLASSIFICATION SYSTEM FOR DYES

Dyes may be classified according to a dual system devised by the Society of

Dryers and Colourists and the American Association of Textile Chemists and

Colorists. Published as the Colour Index, dyes may be classified according to (1)

its chemical class, expressed an assigned number and (2) its usage or application,

expressed through its generic name.

a. Classification by Chemical Class

According to Hunger (2003), the most appropriate system for the classification of

dyes is by chemical structure.

The advantages of classifying dyes by chemical structure are as follows:

1. It readily identifies dyes as belonging to a group that has characteristic

properties. Ex. Azo dyes are known for being strong, good all-round

properties, and cost-effective; while anthraquinone dyes are known for being

weak and expensive.

2. There are a manageable number of chemical groups.

3. It is the classification used most widely by both synthetic dye chemists and dye

technologists.

Page 9: Cyclic Intermediates and Dyes

The twenty-six recognized types of dyes by chemical classification are as follows:

1. Nitroso

2. Nitro

3. Mono-, dis-, tris- and polyazo

4. Azoic

5. Stilbene

6. Carotenoid

7. Diphenylmethane (ketone

imine)

8. Triarylmethane

9. Xanthene

10. Acridine

11. Quinoline

12. Methine and polymethine

13. Thiazole

14. Indamines and indophenols

15. Azine

16. Oxazine

17. Thiazine

18. Sulphur

19. Aminoketone

20. Hydroxyketone

21. Anthraquinone

22. Indigoid

23. Phthalocyanine

24. Natural organic coloring

matters

25. Oxidation bases

26. Inorganic coloring matters

b. Classification by Usage or Application

Shreve enumerates the types of dyes according to its usage or application as

follows:

1. Acid dyes

Dyes termed as acid dyes are derived their name from being insoluble in acid

baths. These dyes are usually azo, triarylmethane or anthraquinone

Page 10: Cyclic Intermediates and Dyes

complexes. Acid dyes are used for dyeing protein fibers such as wool, silk and

nylon. Acid dyes are also used in dyeing leather and paper.

From Knutson’s Synthetic Dyes for Natural Fibers, acid dyes can further

classified into:

e. Leveling acid or strong acid dye

f. Milling or weak acid dyes

g. Super milling or fast acid or neutral acid dyes

2. Azoic dyes

These “ice colors” are made right on the fiber by coupling diazotized materials

while in contact with the fibers. Low temperature keeps the diazonium

compound from decomposing until ready to couple. These are brilliant and

long-lasting and are used primarily for printing on cotton. Rayon, cellulose

acetate, and polyester could also be dyed using azoic dyes.

3. Basic dyes

Basic dyes are mostly amino and substituted amino compounds soluble in acid

and made insoluble by the solution being made basic. Most are triarylmethane

or xanthenes. These can be used to dye wool or cotton with a mordant, but are

usually used for duplicator inks, carbon paper, and typewriter ribbons. In

solvents other than water, they form writing and printing inks. Basic dyes can

also be used on polyacrylonitriles, modified nylons and polyesters.

Page 11: Cyclic Intermediates and Dyes

4. Direct dyes

Direct dyes are water-soluble anionic dyes. These dyes are used to dye cotton

directly, that is, without the addition of a mordant. They are also used to dye

union goods (mixed cotton, and wool, or silk). Other direct dyes are used on

leather, paper, rayon and nylon.These are generally azo dyes, and their

solubility in the dye bath is often reduced by adding salt. Some are developed

on the fiber by forming the diazonium salt on the cloth then coupling to

increase insolubility. Most of the dyes in this class are polyazo compounds,

along with some stilbenes, phthalocyanines, and oxazines.

5. Disperse dyes

Modern synthetics are difficult to dye. Disperse dyes are applied as very finely

divided materials which are adsorbed onto the fibers with which the then form

a solid solution. Simple, soluble azo dyes can be used, but anolamine group is

commonly found in this group and aids both in dispersion and adsorption.

Disperse dyes are substantially water soluble and are used to dye polyester

but they can also be used to dye nylon, cellulose triacetate, and acrylic fibers.

In some cases, a dyeing temperature of 130°C is required, and a pressurized

dyebath is used. The very fine particle size gives a large surface area that aids

dissolution to allow uptake by the fiber. The dyeing rate can be significantly

influenced by the choice of dispersing agent used during the grinding.

Page 12: Cyclic Intermediates and Dyes

6. Reactive dyes

These dyes react to form a covalent link between the dye and the cellulose

fiber which they are customarily used to dye. This produces goods of

outstanding wash-resistance. High-purity reactive dyes are also used in the

ink-jet printing of textiles. Reactive dyes can also be used on rayon and some

nylon. The principal chemical classes of reactive dyes are azo (including

metalized azo), triphendioxazine, phthalocyanine, formazan and

anthraquinone.

7. Fluorescent brightening dyes

Everyone knows what is meant by white, but its accurate definition and

description prove to be quite elusive. “Bluing” has been used for a very long

time to make yellowish laundry appear “whiter”. Greater brilliance can be

obtained with soap, textiles, plastics, paper, and detergents by the addition of

these “optical brighteners”. They absorb ultraviolet light and emit bright blues,

which give greatly improved whiteness. Brighteners are stilbenes with some

pyrazoles, coumarin and naphthalimides as well.

Reflecting pigments such as titanium dioxide are often added to paper to

improve its whiteness. Brighteners are helpful in improving the appearance of

recycled paper.

Page 13: Cyclic Intermediates and Dyes

8. Food, drug, and cosmetic dyes

Food, drug and cosmetic dyes include those coming from anthraquinone, azo

and indigoid classes. Some of these dyes are from the class of carotenoid and

triaryl methane.

9. Mordant dyes

Some dyes combine with metallic salts to form highly insoluble colored

materials called lakes. These materials are usually used as pigments. If a cloth

made of cotton, wool, or other protein fiber is impregnated with an aluminum,

chromium, or iron salt and then contacted with a lake-forming dye, the metallic

precipitate forms in the fiber, and the colors become far more resistant t light

and washing. Substituent groups such as –OH and –COOH attached to azo or

anthraquinone nuclei are capable of reaction with metals to form mordant

dyes.

10. Solvent dyes

Solvent dyes or spirit-soluble dyes are water-insoluble but solvent-soluble

dyes that are devoid of polar solubilizing groups such as sulfonic acid,

carboxylic acid, or quaternary ammonium. These dyes are predominantly azo

and anthraquinone, but phthalocyanine and triarylmethane dyes are also used.

Solvent dyes are used for coloring plastics, gasoline, oils, shoe polishes,

lipsticks, and waxes.

Page 14: Cyclic Intermediates and Dyes

11. Sulfur dyes

Sulfur dyes are a large, low-cost group of dyes which produce dull shades on

cotton. They have good fastness to light, washing, and acids but are very

sensitive to chlorine or hypochlorite.

12. Vat dyes

Vat dyes have chemical structures that are highly complex and most are

derivatives of anthraquinone and indigoid. Upon reduction, they become alkali-

soluble and colorless, and are called leuco vats. Vat dyes are applied mainly

to cellulosic fibers as alkaline bath, usually with sodium hydrogen sulfite.

Vat dyes are expensive and are used to color fabrics (cotton, rayon or wool)

that are washed often like men and women’s shirts. Some vats are supplied as

pastes for printing.

The best known vat dye is the indigo which makes dark (navy) shades. As a

dye for cotton denim, its lack of fastness seems to be prized as a fad.

Page 15: Cyclic Intermediates and Dyes

Table 1: Usage classification of dyes

CLASS PRINCIPAL SUBSTRATES

METHOD OF APPLICATION CHEMICAL TYPES

Acid

nylon, wool, silk, paper, inks and leather

usually from neutral to acidic dyebaths azo (including premetallized), anthraquinone, triphenylmethane, azine, xanthenes, nitro and nitroso

Azoic components and compositions

cotton, rayon, cellulose acetate and polyester

fiber impregnated with coupling component and treated with a solution of stabilized diazonium salt

Azo

Basic paper, polyacrylonitrile,

modified nylon, polyester and inks

applied from acidic dyebaths cyanine, hemicyanine, diazahemicyanine, diphenylmethane, triaryl methane, azo, azine, xanthenes, acridine, oxazine, and anthraquinone

Direct cotton, rayon, paper,

leather, and nylon applied from neutral or slightly alkaline baths containing additional electrolyte

azo, phthalocyanine, stilbene, and oxazine

Disperse polyester, polyamide,

acetate, acrylic and plastics

fine aqueous dispersions often applied by high temperature/pressure or lower temperature carrier methods; dye may be padded on cloth and baked on or thermofixed

azo, anthraquinone, styryl, nitro and benzodifuranone

Fluorescent brighteners

soaps and detergents, all fibers, oils, paints, and plastics

from solution, dispersion or suspension in a mass

stilbene, pyrazoles, coumarin, and naphthalimides

Food, drug and cosmetic

foods, drugs, and cosmetics

----- azo, anthraquinone, carotenoid, and triaryl methane

Mordant wool, leather, and

anodized aluminum applied in conjunction with Cr salts azo and anthraquinone

Reactive cotton, wool, silk, and

nylon reactive site on dye reacts with functional group on fiber to bind dye covalently under influence of heat and ph

azo, anthraquinone, phthalocyanine, triphendioxazine, formazan, oxazine and basic

Solvent plastics, gasoline,

varnishes, lacquers, stains, inks, fats, oils, and waxes

dissolution in the substrate azo, triphenylmethane, anthraquinone, and phthalocyanine

Sulfur cotton and rayon aromatic substrate vatted with sodium

sulfide and reoxidized to insoluble sulfur-containing products on fiber

indeterminate structures

Vat cotton, rayon, and wool water insoluble dyes solubilized by

reducing with sodium hydrogen sulfite, then exhausted on fiber and reoxidized

anthraquinone (including polycyclic quinones) and indigoids

Page 16: Cyclic Intermediates and Dyes

VI. NOMENCLATURE OF DYES

Two ways are available for naming dyes. Dyes are either named by

1. their commercial name or

2. by their Colour Index of C.I.

a. Commercial Name

Commercial names of dyes are usually made up of three parts:

3. A trademark used by the particular manufacturer to designate both the

manufacturer and the class of dye

4. Color

5. Series of letters and numbers used as a code by the manufacturer to define

more precisely the hue and also to indicate important properties of the dye

The common letters used by manufacturers to describe dyes are tabulated below:

LETTER MEANING

Hue R Reddish G Greenish B Bluish Dyeing and fastness properties W Washfast dye E Exhaust dye For solvent and disperse dyes A Lowest level of heatfastness B Mid level of heatfastness C Mid level of heatfastness D Highest level of heatfastness For reactive dyes M Warm-dyeing dye H Hot-dyeing dye

Page 17: Cyclic Intermediates and Dyes

There are instances when some manufacturers designate a bluish red dye as Red

4B while other manufacturers use Violet 2R for the same dye. TO resolve such

problem, it is better to consult the pattern leaflets provided by the manufacturing

company.

b. Colour Index (C.I.)

It is not uncommon for a single dye to have multiple names if one follows the

nomenclature of dyes using the method in the previous section. The term fuchsin

was once called magenta and light green can also be called methyl green. To

avoid further confusion, it is better to use the Colour Index method in naming dyes.

The Colour Index or CI is basically a compendium of dyes prepared by the Society

of Dyers and Colourists and the American Association of Textile Chemists and

Colorists as previously mentioned under the Classification of Dyes. The CI comes

in a book and a CD form and it presents a specific system to identify individual

dyes.

Page 18: Cyclic Intermediates and Dyes

The general way of identifying dyes using the Colour Index is given below.

The CI generic name (CI Name) identifies dyes using the pattern given above. Its

syntax is given as CI <application type> <hue> <identifying number>. Using the CI

Name enables the easy identification of the hue and dye type at a glance. The CI

Name, however, may vary from one manufacturer to another. A dye dubbed as CI

Direct Blue 99 from one company may not be identical to the CI Direct Blue 99 of

another company.

The CI number (Constitution number) identifies dyes following a specific,

identifying, five-digit number code. It is assigned to a dye when its chemical

structure has already been identified by the manufacturer. Dyes with similar

chemical class or structures are given similar CI numbers. The CI number is

Page 19: Cyclic Intermediates and Dyes

generally used when identifying dyes to be used in staining methods to avoid

confusion.

An illustration of using both CI Name and CI Number to name a dye is shown

below.

Chemical structure:

Molecular formula: C33H20O4

Chemical Abstracts name: 16, 17-dimethoxydinaphthol[1,2,3-cd:3',2',1'-Im

perylene-5,10-dione]

Trivial name: jade green

C.I. name: C.I. Vat Green I

C.I. number: C.I. 59825

Application class: vat

Chemical clas : anthraquinone

CAS registry number: [128-58-5]

Commercial names: Solanthrene Green XBN, AVECIA,

Cibanone Brilliant Green, BF, 2BF, BFD,

CIBA-GEIGY Indanthrene Brilliant Green, B, FB

Page 20: Cyclic Intermediates and Dyes

VII. EQUIPMENT AND DESIGN

The basic steps of dye (and intermediate) manufacture are shown below.

a. Reaction

The reactions involved in this step may either be as follows:

a. sulfonation,

b. halogenations,

c. amination,

d. diazotization, and

e. coupling

The reactor itself is usually the focal point of the plant, but this does not mean that

it is the most important part of the total manufacture, or that it absorbs most of the

capital or operational costs. The processes after the reaction are often termed as

workup stages. Workup stages differ from one product to another. For example,

intermediates require less finishing than dyes.

The specifications for the reaction vessel for the production of intermediates and

dyes are as follows:

Materials Charging

Reaction

Product Isolation

Product drying, grinding, and/or

finishing

Page 21: Cyclic Intermediates and Dyes

a. The reaction is carried out in a bomb-shapes reaction vessel.

b. The reaction vessel may be made from cast iron, stainless steel, or steel lined

with rubber, glass (enamel), brick, or carbon blocks.

c. The volume of the reaction vessel is between 2-40 m3 (500-10 000 gallons).

d. The reaction vessel must be equipped with mechanical agitators,

thermometers, or temperature recorders, condensers, pH probes, and etc.

depending on the nature of the operation.

Jackets or coils may be used for the heating and cooling of the reactor. High-

boiling fluids (e.g. hot oil or Dowtherm), steam, or hot water may be used to raise

the temperature; while air, cold water, or chilled brine may be used to lower it.

Unjacketed vessels are often used for reactions in aqueous solutions. Heating may

be done through direct introduction of steam, and cooling may be done by addition

of ice. Heat exchangers can also be used. The reaction vessels normally span two

or more floors in a plant to facilitate ease of operation.

b. Product Isolation

Products are transferred from one piece of equipment to another by gravity flow,

pumping, or blowing with air or inert gas. Solid products are separated from liquids

using any of the following methods:

a. centrifuge

b. filter boxes

c. continuous belt filters

Page 22: Cyclic Intermediates and Dyes

d. various designs of plate-and-frame or recessed-plate filter presses

c. Product drying, grinding, and/or finishing

In some cases products, usually in the form of pastes discharged from a filter, must

be dried. Even with optimization of physical form, the water content of pastes

varies from product to product in the range of 20-80 %.

Among the different drying methods employed are the following:

a. air or vacuum ovens

b. rotary dryers

c. spray dryers

d. drum dryers

The final stage in dye manufacture is grinding or milling. Dry grinding is usually

carried out in impact mills; considerable amounts of dust are generated and well-

established methods are available to control this problem. Dry grinding is an

inevitable consequence of oven drying, but more modern methods of drying,

especially continuous drying, allow the production of materials that do not require a

final comminution stage. The ball mill has been superseded by sand or bead mills.

Wet milling has become increasingly important for pigments and disperse dyes.

Many patented designs, particularly from Draiswerke GmbH and Gebruder

Netzsch, consist of vertical or horizontal cylinders equipped with high-speed

Page 23: Cyclic Intermediates and Dyes

agitators of various configurations with appropriate continuous feed and discharge

arrangements.

Figure 1 below shows the layout of a typical azo dye manufacturing plant.

Figure 1: Layout of azo dye manufacturing plant. 1, storage tanks for liquid starting

materials; 2, storage drums for solid starting materials; 3, diazotisation vessel; 4,

coupling component vessel; 5, ice machine; 6, coupling vessel; 7. isolation vessel; 8.

filter presses; 9, filtrate to waste liquor treatment plant; 10, dryers; 11, emptying of

dyestuffs for feeding to the mill; 12, outgoing air purification plant.

d. Waste Characteristics

The principal air pollutants from dye manufacturing are as follows:

Page 24: Cyclic Intermediates and Dyes

a. volatile organic compounds (VOCs),

b. nitrogen oxides (NOx)

c. hydrogen chloride (HCl)

d. sulfur oxides (SOx)

Liquid effluents from the cleaning of the equipments after batch operation can

contain toxic organic residues. Cooling water are normally recirculated.

Wastewater generation rate is usually 1-700 liters/kg of product except for vat

dyes. Vat dye production can generate wastewater of up to 8,000 L/kg of product.

Major solid wastes include:

a. filtration sludge

b. process and effluent treatment sludges

c. container residues

Other wastes that are considered toxic are,

a. wastewater treatment sludges

b. spent acids

c. process residues from the manufacture of chrome yellow and orange pigments,

molybdate orange pigments, zinc yellow pigments, chrome and chrome oxide

green pigments. Iron blue pigments and azo dyes

Page 25: Cyclic Intermediates and Dyes

VIII. REFERENCES

Shreve, R. and Austin, G. Shreve’s Chemical Process Industries, 3rd ed. McGraw-Hill

Publishing, Inc. 1984

Hunger, K. Industrial Dyes, Chemistry, Properties, Applications, Wiley-VCH, 2003

http://www.uploadcity.com/?f=8837762&t=Fundamentals_of_Biochemical_Engineering.rar&

http://www.ifc.org/ifcext/enviro.nsf/AttachmentsByTitle/gui_dye_WB/$FILE/dye_PPAH.pdf

http://www.pburch.net/dyeing/aciddyes.shtml

http://www.morechemistry.com/publ/colours_dyes/slide094.html

http://www.dyespigments.com/colour-index.html

http://www.globalspec.com/reference/41765/203279/Nomenclature-of-Dyes

http://www.dyespigments.com/what-is-dye.html

http://218.6.128.157/excellentcourses/fccae/pdf_textbook/3_jxh_Dyes-a%20general%20servy

.pdf


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