Epidermal trichomes of the seeds of cultivated species of the Gossypium herbaceum and other species of Gossypium (G. hirsutum, G. barbadense) freed from impurities, fats and sterilized, belonging to family Malvaceae.
COTTON
Synonyms
Raw cotton, purified cotton, absorbent cotton.
Biological Source
Epidermal trichomes of the seeds of cultivated species of
the Gossypium herbaceum and other
species of Gossypium (G. hirsutum, G. barbadense) freed from
impurities, fats and sterilized, belonging to family Malvaceae.
Geographical Source
United States, Egypt, some parts of Africa, and India.
History
There are about 39 species of Gossypium worldwide which are native to the tropics and warm
temperate regions. Three species are native to South Africa, of these, Gossypium hirsutum from Mexico has
become the predominant species in commercial
cotton production worldwide. About 90% of the world commercially produces
cotton from G. hirsutum. G. barbadense contributes
to 8% of the market while the remaining
2% belongs to the old world cotton grown in South and South-East Asia.
Gossypium
herbaceum or the African-West Asian cotton: Gossypium herbaceum is the indigenous species in India.
It is native to semidesert conditions
like in sub-Saharan Africa and in Arabia. It is a perennial shrub. It is widely
cultivated in Ethiopia and also in Persia, Afghanistan. Turkey, North Africa,
Spain, Ukraine, Turkestan, and China (first cultivation in China reported was
in about A.D. 600). It reaches a height of 2–6 feet, with palmate hairy leaves,
lobes lanceolate, acute yellow petals and a purple spot in centre, capsule when
ripe splits itself and exposes the loose white clump surrounding the seeds and
strongly adhering to the outer coating. G.
herbaceum requires warm weather to
ripen its seeds.
Gossypium
arboreum or the Pakistani-Indian cotton: It is native to Northwest India and
Pakistan. The use and production of cotton dates back to 2000 BC, by the
Harappan civilization of the Indus Valley. Some of them are tall perennial
while others are short annuals. People of Nubia are considered to be the first
cotton weavers of Africa. This cotton variety extended into other parts of
Africa (Nigeria) that became a cotton-manufacturing centre from the 9th century
onwards.
Gossypium barbadense or South American cotton: G.
bar-badense gives
the Sea Island, or long-stapled cotton. The
oldest cotton textiles recorded from South America date to 3600 B.C. The
first sign of domestication of cotton species comes from Peruvian coast where
cotton bolls dating to 2500 B.C. were found. Cotton became a commercial slave
plantation crop in the West Indies and as a result of it Barbados in 1650s
became the first British West Indian colony to export cotton. Later on around
1670, planting of G. barbadense also
began in the British North American colonies.
Gossypium
hirsutum or Mexican cotton: G. hirsutum are found
in coastal vegetation of Central and Southern North America and also in the
West Indies. There are evidences of cotton remains dating back to 3500 B.C. in
the Tehuacan Caves in Mexico and even the Spanish explorers have found cotton
cultivation in the 1500s.
Cultivation, Collection, and Preparation
Cotton is cultivated by means of seed sowing method. The
seeds are sown in rows of about 4–5 ft in distance. Proper fertilizers are
provided timely. The cotton plants are shrubs or small trees that bare fruits
(capsules) after flowering. The capsule consists of three to five seeds and is
covered with hairs. The bolls are collected when ripe, separated from the
capsule, dried, and subjected to the ginning press for processing. In ginning
process, hairs and seeds are put before the roller with a small space, which
separates the trichomes from the seeds. The short and long hair separated by
delinter. Short hairs are known as ‘linters’, which are used in the
manufacturing inferior grade cotton wool, whereas long hairs are used for
preparation of cloth. The seeds remain after the removal of hair is used for
the preparation of cotton seed oil and oil cake for domestic animal feed. The
raw cotton so obtained is full of impurities like the colouring matter and
fatty material. It is then subjected to further purification by treating it
with dilute soda ash solution under pressure for about 15 hours. It is then
bleached and washed properly, dried, and packed. The packed cotton is then
sterilized using radiations.
Description
Chemical Constituents
It consists of 90% of cellulose, 7–8% of moisture, wax, fat
and oil 0.5% and cell content about 0.5%. Purified cotton has almost cellulose
and 6–7% of moisture.
Chemical Tests
1. On ignition, cotton burns with a flame,
gives very little odour or fumes, does not produce a bead, and leaves a small
white ash; distinction from acetate rayon, alginate yarn, wool, silk, and
nylon.
2. Dried cotton is moistened with N/50
iodine and 80% w/w sulphuric acid is added. A blue colour is produced;
distinction from acetate rayon, alginate yarn, jute, hemp, wool, silk, and
nylon.
3. With ammoniacal copper oxide
solution, raw cotton dissolves with ballooning, leaving a few fragments of
cuticle. Absorbent cotton dissolves completely with uniform swelling,
distinction from acetate rayon, jute, wool, and nylon.
4. In cold sulphuric acid (80% w/w)
cotton dissolves; distinction from oxidized cellulose, jute, hemp, and wool.
5. In cold sulphuric acid (60% w/w)
cotton, is insoluble; distinction from cellulose wadding and rayons.
6. In warm (40°C) hydrochloric acid it
is insoluble; distinction from acetate rayon (also silk, nylon).
7. It is insoluble in 5% potassium
hydroxide solution; distinction from oxidized cellulose, wool, and silk.
8. Treat it with cold Shirla stain A
for 1 min and wash out. It shows shades of blue, Tilac or purple; distinction
from viscose, acetate rayons, alginate yarn, wool, silk, and nylon.
9. Treat it with cold Shirla stain C
for 5 min and wash out; raw cotton gives a mauve to reddish-brown colour and
absorbent cotton a pink one; distinction from flax, jute, hemp. The Shirla
stains may be usefully applied to a small piece of the whole fabric under
investigation to indicate the distribution of more than one type of yarn.
10. It does not give red stain with
phloroglucinol and hydrochloric acid; distinction from jute, hemp, and kapok.
Uses
Cotton is used as a filtering medium and in surgical
dressings. Absorbent cotton absorbs blood, pus, mucus, and prevents infections
in wounds.
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