sugar, any of sweet, colourless, water-soluble compound present in the sap of seed plants and

the milk of mammals and making up the simplest group of carbohydrates. As a chemical term,
“sugar” usually refers to all carbohydrates consisting of carbon (C), oxygen (O), and hydrogen (H)
atoms of the general formula Cn(H2O)n. The most common sugar is sucrose, a crystalline tabletop
and industrial sweetner used in foods and beverages.
Classification of sugar
There are three main groups of sugars, classified according to the way the atoms are arranged
together in the molecular structure. These groups are the following:

 Monosaccharides or simple sugars. are often referred to as simple sugars consisting of a

single sugar molecule (e.g., glucose, fructose, galactose) and cannot be hydrolyzed into
simpler compounds.
 Monosaccharides can be subdivided based on the number of carbon (C) atoms. The
following list shows the prefixes for numbers of carbons in a sugar.
 Disaccharides or complex sugars. They are formed when two monosaccharide are joined
together through a glycosidic bond. Sucrose (common sugar) is the primary example of a
disaccharide. Composed of glucose and fructose.
 Polysaccharides. They are long chains of many monosacharids liked togther. Examples
are starches, dextrins, and cellulose.
Structure of sugar
Carbohydrates can be represented by the stoichiometric formula (CH 2O)n, where n is the
number of carbons in the molecule. In other words, the ratio of carbon to hydrogen to oxygen is
1:2:1 in carbohydrate molecules.

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The chemical structure of monosaccharides can be represented as a straight chain form( as seen
above) and in cyclic form In a biological system, glucose exists primarily as a cyclic form and
very rarely in a straight form.

cyclic form of glucose

DISACCHARIDES

Lactose

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 Structure of polysaccharide

Sources of sugar
Monosaccharides.
The common sources of monosaccharides are Honey, fruits such as apples, dates, cereals, oats
and fruits, vegetables (sweet corn), manufactured foods such as juices, cured hams, pasta sauces,
Digestion and conversion of other carbohydrates.
 Derived from sugar cane and sugar beet,table sugar, manufactured foods, such as cakes,
cookies, and dark chocolate, Sweet root vegetables such as beetroot and carrots, Breads,
Malt extract, Beer, buttermilk, yogurt, sour cream, condensed milk, Milk products lik
frozen yogurts, evaporated milk, goats milk & ice creams, Mushrooms and edible fungi
polysaccharides can be found from
1.Starch (Cereal foods, cornmeal, pretzels, flours, oats, instant noodles, pasta, rice, Potato, corn
Small amounts in other root vegetables and unripe fruit).
2.Non-starch polysaccharides Vegetables, fruit, Wholegrain cereals etc.
Importance/Uses of Sugars.
Uses
1.Sugar is an important nutrient that serves as a source of energy( As foods break down, first
through digestion and then in the cells, the chemical bonds which hold glucose molecules
together break as well. This action releases energy, and this energy fuels all our bodily functions)

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2. It is crucial to maintaining physiological functions. As such parts of the body as the brain,
nerves, and red blood cells are unable to use any sugars other than the monosaccharide glucose.
3. It also has a diverse array of other functions, including acting as a preservative, as it inhibits
lipid oxidation, starch retrogradation, and protein denaturation.
4.Economic uses
Sugarcane is the source of 80%-85% of the world’s sugar supplies, with the other 15% derived
mainly from sugar beet and corn starch.
5 Apart from uses in foodstuffs, sugarcane is also used in the manufacturing of products such as
ethanol, animal stock feed, fertilisers, paper, plastics and various types of chemicals.
Effect of excessive sugar intake
Even though we need carbohydrates to keep our bodies going, and even though sugars are the
easiest carbs to use for energy, a diet filled with extra sugar is never recommended.
Our bodies get all the sugar they need from the natural sugar in the foods we eat and along with
that sugar come vitamins, minerals, antioxidants, fiber, and/or protein. Extra sugars added during
baking or mixing or processing for flavor and sweetness provide none of these nutrients. These
sugars are known as “added sugars,” and have more serious consequences than just empty
calories.Once we have the sugars we require, there’s no need for more. Extra sugars are stored in
liver, muscle, and fat cells for later use. When we eat too much sugar, this carefully balanced
system is upset, with negative effects for human halth like weight, blood sugar, insulin levels—
and our dental health.
Manufacture of Cane Sugar
Procedures of manufacture of sucrose from cane sugar are as follows:
1) Extraction of juice (2) Purification of juice (3) Concentration of juice (4) Crystallization
(5) Separation of crystals (6) Drying and bagging
Extraction of Juice: The cane is washed,cut into small lengths with knives, fitted on a
horizontal shaft and then dropped over a moving belt, called cane carrier to the extractor
consisting of crusher where they pass through the rollers to extract about 50% of the juice. The
bagasse containing 50% of the juice is then introduced into the mill. Juice extracted in the mill
is collected and transferred to the raw juice tanker. About 90-96% juice is extracted from the
cane and the spent cane baggasse is collected in the storage which is burned as fuel or is used in
the manufacture of paper or insulating material.
Purification of Juice: The liquor prepared for filtration and classification by removing solid
impurities. The juice is at once transferred into defection tank, neutralized by adding adequate
amount of milk of lime (Ca (OH) 2) till the pH reaches 7-7.3 and heated to boiling. The hot
limed juice is then poured into settling tanks, where it separates into three layers. The upper
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layer, the middle layer (clear juice) and heavy bottom layer. The top and bottom layers are
removed mechanically by passing through a filter press. By crystallizing the concentrated
juice called syrup, a coloured, crystalline sugar (raw sugar) is obtained. The raw sugar is then
clarified by conversion into white crystalline sugar by a refining process.
Concentration: The clarified juice is concentrated into thick syrup under reduced pressure in
multi effect vacuum evaporators. From the last evaporator in the multi effect vacuum
evaporators, pale yellow thick syrup is led into the syrup tank as concentrated raw sugar. The
syrup liquid is further concentrated by removing most of the water by heating in a single effect
evaporator called vacuum pan.
Crystallization: The concentrated syrup is then led to crystallizing tanks and cooled slowly
when crystals of sugar separate out.
Separation of Crystals: Crystals of sugar are then separated from molasses (mother liquor) by
whirling in centrifugal machine. As a result of high revolving motion, the crystals are easily
separated and liquid portion drains out.
Drying: The crystals of raw sugar obtained after centrifuging are dried by dropping them in a
long pipe through which hot air or superheated steam is passed and finally bagged.

Vanishes
A vanish is homogneous liquid containing essentially a resinous substance dissolvedin a suitable
oil or volatile liquid.Or a vanish is a transparent liquid which is usd to provide a protective
surface coating. A vanish does not contain any pigment.However it is always used as a finishing
coat.
VARNISHES
Varnish is a solution of some resinous substance in alcohol, oil or turpentine. The process of
covering the surface with varnish is known as varnishing. Varnishing is done only on wooden
surface.
Functions of Varnish
Varnish performs the following functions:
(i) It imparts a delicate brilliance on painted surface.
(ii) It is used as a decorative and protective covering of surfaces against adverse
effects of the atmosphere.
(iii) It increases the durability of the paint film.
(iv) It beautifies the surface without hiding the beautiful grains of the wood.

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Constituents of the Varnish
A varnish is composed of three elements
Film Forming Materials:: These are drying oils and resins. The resin of varnish may be
natural or artificial. Natural resins used in varnishes include rosin, copal,shellac and amber
while synthetic resins include phenyl and vinyl resins. The purpose and function of the
film forming materials is to form protective film and binders for pigments when the
solvents are evaporated and the varnish oil is dried. Quality of varnish depends much upon
the quality of resin used.
Driers
Driers are used to accelerate the process of drying of the varnish. Litharge, acetate, and
white copper are the various types of driers, out of which litharge is mostly used.
Solvents
These are necessary for dissolving the resins and control of flow characteristics i.e. viscosity of
film-forming materials. The common solvents used are linseed oil, turpentine oil, petroleum
spirits, kerosene, dipentene, aromatic and aliphatic naphtha, xylol, alcohols, etc.
Selection of solvent is made depending upon the type of resin.

S/No. Name of Resin Solvent Used

1 Amber and copal Linseed oil
2 Lac Methylated spirit
Chemistry behind varnishes
Most varnishes are a blend of resin, drying oil, drier, and volatile solvent. When varnish dries, its
solvent portion evaporates, and the remaining constituents oxidize or polymerize to form a
durable transparent film. After being applied, the film-forming substances in varnishes either
harden directly, as soon as the solvent has fully evaporated, or harden after evaporation of the
solvent through curing processes, primarily chemical reaction between oils and oxygen from the
air(autoxidation) and chemical reactions between components of the varnish.

Types of Varnish
The varnishes can be classified into following categories depending upon the solvent
used:
Oil Varnish
These are varnishes in which linseed oil is used as solvent. This type of varnish is manufactured
by dissolving hard resins such as amber and copal in linseed oil. Turpentine may be used in
small quantity to thin the varnish, and also to render it workable. Although they dry slowly,

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they form a hard and durable film, making them a popularly used in external finish. They are
quite resistant to weather change.
Spirit Varnishes: These are varnishes in which methylated spirit or other completely volatile
non film forming solvent is used as solvent They are usually made from natural resins such as
shellac, rosin, copal, damer, kauri gum etc. These varnishes dry more rapidly but undergo
cracking and peeling and gets easily affected by weather action. This varnish is mostly used for
wood furniture to protect them from rain, gasses and light.
Turpentine Varnish
In this type of varnish, gum, dammar, mastic, and rosin like resins are dissolved in turpentine.
These varnishes are light in colour and dry quickly.
Water Varnish
This varnish is prepared by dissolving shellac in hot water. Shellac does not dissolve readily in
water and as such to accelerate the process of dissolving shellac in water either ammonia or
potash, or soda or borax is added. This varnish is used for painting pictures, posters and maps.
Asphalt Varnish
This varnish is obtained by dissolving melted asphalt in linseed oil. The varnish may be
thinned by adding suitable amount of either turpentine or petroleum spirit. This varnish is
used for varnishing fabricated iron and steel product.
Spar Varnish
This varnish derives its name from its use. It is mostly used on spars and other exposed parts of
the ships. It is very good weather resistant. It should not be used indoor.
Flat Varnish
This is an ordinary varnish to which material such as wax, finely divided silica and metallic
soaps are added, to reduce the gloss of the varnished surface. This varnish presents a dull
appearance.
PLASTICS
The name plastic denotes materials containing higher molecular resins as their main
component, which are capable of changing into a plastic state at high temperatures and
pressures.
Plastics have excellent mechanical strength. Plastics are excellent insulators, stable to
aggressive media, and have a low thermal conductivity.
Plastic can either be ‘synthetic’ or ‘biobased’. Synthetic plastics are derived from crude oil,
natural gas or coal. Whilst biobased plastics come from renewable products such as
carbohydrates, starch, vegetable fats and oils, bacteria and other biological substances.

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The vast majority of plastic in use today is synthetic because of the ease of manufacturing
methods involved in the processing of crude oil.
Most of the plastic in use today is derived by the following steps:
1. Extraction of raw materials (largely crude oil and natural gas, but also coal) – these are a
complex mixture of thousands of compounds that then need to be processed.
2. Refining process transforms crude oil into different petroleum products – these are
converted to yield useful chemicals including “monomers”. In the refining process, crude oil is
heated in a furnace, which is then sent to the distillation unit, where heavy crude oil separates
into lighter components called fractions. One of these, called naphtha, is the crucial compound
to make a large amount of plastic. However, there are other means, such as using gas.
Polymerisation is a process in the petroleum industry where light olefin gases (gasoline) such
as ethylene, propylene, butylene (i.e., monomers) are converted into higher molecular weight
hydrocarbons (polymers). This happens when monomers are chemically bonded into chains.
There are two different mechanisms for polymerisation:
A. Addition polymerisation
The addition polymerisation reaction is when one monomer connects to the next one (dimer)
and dimer to the next one (trimer) and so on. This is achieved by introducing a catalyst,
typically a peroxide. This process is known as chain growth polymers – as it adds one monomer
unit at a time. Common examples of addition polymers are polyethylene, polystyrene and
polyvinyl chloride.
B. Condensation polymerisation
Condensation polymerisation includes joining two or more different monomers, by the removal
of small molecules such as water. It also requires a catalyst for the reaction to occur between
adjacent monomers. This is known as step growth, because you may for example add an
existing chain to another chain. Common examples of condensation polymers are polyester and
nylon.
Compounding/Processing
In compounding, various blends of materials are melt blended (mixed by melting) to make
formulations for plastics. Generally, an extruder of some type is used for this purpose which is
followed by pelletising the mixture. Extrusion or a different moulding process then transforms
these pellets into a finished or semi-finished product. Compounding often occurs on a twin-
screw extruder where the pellets are then processed into plastic objects of unique design,
various size, shape, colour with accurate properties according to the predetermined conditions
set in the processing machine.
Advantages of plastics

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 a) Their high resistance to the effects of environmental factors and various corrosive
media.
b) Their capability of being processed into ware of complex shapes by the most efficient
modern methods.
Disadvantages of plastics
a) Their low resistance to heat as compared to metals; most plastics can be used only at
temperature up to 150oC and get deformed thereafter..
b) Most plastics undergo aging as a result of oxidation, darkening, reduction of hardness
and strength.
CLASSIFICATION OF PLASTICS
Plastic materials are classified into two classes, namely: thermosetting and
thermoplastic, according to the manner of setting
1) Thermosetting Plastics: Thermosetting plastics are those which change irreversibly
into hard and rigid materials on heating. After cooling, if the set article is again
heated, it will not soften again, hence it is irreversible. Thermosetting resins are
usually harder, stronger, and more brittle than thermoplastic resins and they cannot be
reclaimed from waste. The resins are formed by condensation polymerization. They
are almost insoluble in all organic solvents, due to cross-linking and strong bonds.
Examples of thermosetting plastics are phenol formaldehyde plastic or bakelite,
amino plastics and alkyd plastics, epoxy plastics, etc.
2) Thermoplastic Plastics: These plastics or resins soften on heating and regain their
original properties on cooling. Their hardness is a temporary property subject to
change with increase or decrease in temperature. Repeated heating or cooling does not
alter the chemical nature of thermoplastic resins, because the changes involved are of
physical nature. They soften on heating and remain soft as long as they are hot. They
regain their original rigidity and hardness on cooling. Thermoplastic resins are usually
soft, weak and less brittle and can be reclaimed from the wastes. These resins are
formed by addition polymerization only and consist of long chain linear polymers
with little or no cross linking. These resins are usually soluble in some organic
solvents. Examples of thermoplastic plastics are cellulose nitrate, cellulose acetate
butyrates, ethyl cellulose, polyacrylates, polyvinyl resins, styrene or polystyrene
resins, polyamides (nylon), polyethers, polypropylene, polyethylene etc.