WET PROCESSING-I (pre-treatment)

Prepared by-

KHURSHEDUL ALAM, Begumganj Textile Engineering College, 2nd

batch.

Email:khurshed_btec2012@yahoo.com.

ACID, ALKALI & SALT

Q. DEFINE ACID.

Ans:

The compound containing hydrogen atom which are replaced by metal or metal like

activated radical & produce salt & water is called acid.

On the other hand, we can say, the hydrogen containing compound which are ionized in

water & produce hydrogen ion as a positive ion is known as acid.

Example: H2SO4, HCl, HNO3 etc.

Q. WRITE THE PROPERTIES OF ACID. Noakhali textile- ’08.

Ans: Properties:

1. Acid ionized in water & produce hydrogen ion.

HCl = H + + Cl

-

H2SO4 = 2 H+ + SO4-

2. In the presence of hydrogen ion, acid changes the color of litmas from blue to red. Blue

litmas + H+ = red litmas.

3. Acid reacts with alkali & produce salt & water.

HCl + NaOH = NaCl + H2O.

NaOH + H2SO4 = NaHSO4 + H2O

NaHSO4 + NaOH = Na2SO4 + H2O.

4. The taste of acid is sour.

5. Acid reacts with strong metal such as Mg, Al, Zn & produce Hydrogen gas.

2 HCl + Mg = MgCl2 = MgCl2 + H2.

Q. WRITE THE USES OF ACID IN WET PROCESSING OF TEXTILE.

Ans:

1. Acid is used in scouring process (HCl).

2. H2SO4 is used to soften hard water in case of demineralization or ion exchange process.

3. HCl is used in carbonizing of wool.

4. H2SO4 is used in spgn process of viscose rayon.

5. Acids are used for dyeing of protein fibre with acid dye.

6. HCl is used to dissolve the di-azo compound.

7. H2SO4 is used for fermentization.

8. H2SO4 (conc.) is used for neutralizing mercerized product.

9. Acetic or formic acid is used to adjust pH of dye bath.

10. Acids are used for washing purpose.

11. H2SO4 or HCl is used for acid steeping.

WET PROCESSING-I (pre-treatment)

Prepared by-

KHURSHEDUL ALAM, Begumganj Textile Engineering College, 2nd

batch.

Email:khurshed_btec2012@yahoo.com.

Q. CLASSIFY ACID. Noakhali textile- ’08

Ans:

A) On the basis of constitution: i) HYDRO ACID: The acids which contain Hydrogen atom are called hydro acid.

Example: HCl, HCN etc.

ii)OXI ACID: The acids which contain oxygen & Hydrogen atom are called oxi acids.

Example: H2SO4, HNO3 etc.

B) On the basis of origin:

i) ORGANIC: The acids which are obtained from animals & vegetables are called

organic acids. Example: acetic acid, formic acid etc.

ii) INORGANIC: The acids which are obtained from mineral are called inorganic acids.

Example: HCl, H2SO4 etc.

C) On the basis of strength:

i) STRONG ACID: The acids which are fully ionized in water & produce large amount

of H+

are called strong acid. Example: H2SO4, HCl etc.

ii) WEAK ACID: The acids which are partially ionized in water & produce large

amount of H+

are called weak acid. Example: HCOOH.

D) On the basis of alkalinity:

i) MONO ALKALINE ACID: The acid which are contains only one Hydrogen atom is

called mono alkaline acid. Example: HCl, HCN etc.

ii)DI-ALKALINE ACID: The acid which contains two replaceable Hydrogen atom is

called di-alkaline acid. Example: H2SO4.

iii) TRI-ALKALINE ACID: The acid which contains three replaceable Hydrogen

atom is called tri-alkaline acid. Example: H3PO4.

Q. DEFINE ALKALI.

Ans: The compounds which contain oxide (O2-

) or hydroxide ion, react with acids & produce

salt & water are known as alkali. Alkalis are ionized in water & produce hydroxyl ion (OH -).

Example: NaOH, KOH etc.

Q. WRITE DOWN THE PROPERTIES OF ALKALI. Noakhali textile- ’08.

Ans:

Properties:

1. Alkalis are too much soluble in water.

2. It is ionized in water & produce hydroxyl ion (OH -).

NaOH = Na+ + OH

-

3. It changes the color of litmas from red to blue.

Red litmas + H+ = blue litmas.

WET PROCESSING-I (pre-treatment)

Prepared by-

KHURSHEDUL ALAM, Begumganj Textile Engineering College, 2nd

batch.

Email:khurshed_btec2012@yahoo.com.

4. It reacts with acid & produce salt & water.

HCl + NaOH = NaCl + H2O.

5. The alkaline soln of alkali damage organic substances or life cells.

Q. WRITE THE USES OF ALKALI IN WET PROCESSING OF TEXTILE. Noakhali textile- ’08.

Ans: Uses:

1. NaOH is used in scouring & mercerizing of textile wet processing.

2. NaOH is used in the production of viscose rayon from cellulose.

3. NaOH is used to produce paper, petroleum & in the laboratories as reagent.

4. Ca(OH2) is used to produce bleaching powder.

5. Ca(OH2) is used to remove the hardness of water.

6. NaOH & Ca(OH2) are used in various washing purposes.

Q. DEFINE SALT.

Ans: When Hydrogen atom of acid is fully or partly replaced by the metal or metal like reactive

radical, then the compound which is found is known as salt.

Example: NaCl, KNO3, CaCl2 etc.

Q. STATE THE PROPERTIES OF SALT. Noakhali textile- ’08.

Ans: Properties:

1. The test & color of different salts are different.

2. The colors of salts are generally white, green, blue, yellow, red etc.

3. The solubility of different salts are different.

4. In water, it is ionized & produce +ve & -ve ion.

NaCl (dissolved in water) = Na+ + Cl

-

5. Each salt contains an acidic & a basic radical.

Q. CLASSIFY SALT. Noakhali textile- ’08.

Ans: Salts are classified into following six types according to the construction:

1. Normal salt: The salt which is produced by replacing the Hydrogen atom of acid by metal

or metal like active radicals is known as normal salt. Ex.: ZnSO4, KNO3, NaCl etc.

2 Na + 2 HCl = 2 NaCl + H2.

2. Acid salt: The salt which is produced by replacing the Hydrogen atom partly by metal

like active radicals is known as acid salt. Ex.: NaHSO4.

NaOH + H2SO4 = NaHSO4 + H2O.

3. Basic salt: If the amount of acid to produce normal salt with certain amount of base is less

than the salt is called basic salt. Ex.: [CaCO3.Ca(OH)2].

WET PROCESSING-I (pre-treatment)

Prepared by-

KHURSHEDUL ALAM, Begumganj Textile Engineering College, 2nd

batch.

Email:khurshed_btec2012@yahoo.com.

4. Mixed salt: The salt which is produced by replacement of more than one Hydrogen atom

by more than one different types of metals is called the mineral salt. Ex.: NaKCO3.

5. Couple salt: When two normal salts are mixed together in their soln at same ratio, then this

salt is called couple salt. Ex.: [K2SO4.Al2(SO4)3.24H2O].

6. Complex salt: If two different normal salts are mixed at a certain ratio, where the mixed

compound has the properties different from the two normal salts, then the salt, which is

produced is called complex salt. Ex.: [K4Fe(CN)6].

Q. WRITE THE USES OF SALT IN WET PROCESSING OF TEXTILE. Noakhali textile- ’08.

Ans: Uses:

1. Na2SO4 is used for the finishing of cotton is also for dyeing of direct & sulpher dyes.

2. NaHSO4 is used for washing of silk & wool.

3. Na2SO4 is used to remove the color of silk, wool & cotton.

4. NaOCl is used in bleaching.

5. Ca(OCl)Cl is used in cotton bleaching.

6. NaClO3 is used in bleaching, dyeing & printing.

7. Na2S is used to make the soln of sulpher dye.

WET PROCESSING-I (pre-treatment)

Prepared by-

KHURSHEDUL ALAM, Begumganj Textile Engineering College, 2nd

batch.

Email:khurshed_btec2012@yahoo.com.

8. IMPURITIES

Q. CLASSIFY IMPURITIES.

Ans: Impurities are the substance which is present in textile mtl, but they are not useable.

Impurities are mainly four types-

a) Inherent / growth impurities.

b) Advantitious impurities.

c) Picked up impurities.

d) Additive impurities.

Q. STATE THE CHEMISTRY OF VARIOUS IMPURITIES IN DIFFERENT FIBRE &

THEIR WAY OF REMOVAL. Noakhali textile- ’08.

Or, STATE THE IMPURITIES OF COTTON & THEIR REMOVAL PROCESS. Noakhali textile- ’09.

Ans: Cotton: The main ingredient of cotton is cellulose (94%). It also contains many other

component which is known as cotton impurities.

Impurities Percentage (%) Removal process

Protein 1.3 Scouring

Pectin 1.2 Scouring

Mineral matter 1.3 Scouring

Oil, fat & waxes 0.6 Scouring

Ash 0.5 Scouring

Others 1.1 Scouring

Jute: Jute is cellulosic bast fibre. The main ingredient of jute is cellulose (94%). It also contains

many other component which is known as jute impurities.

Impurities Percentage (%) Removal process

Hemi-cellulose 22.2 Mild scouring

Lignin 10.8 Mild scouring

Water slabs 1.50 Mild scouring

Fat, waxes & color pigment 0.5 Fat → scouring,

Color pigment→ bleaching.

Wool: Wool is an animal fibre. The main ingredient of wool is keratin (61%). It also contains

many other component which is known as wool impurities.

Impurities Percentage (%) Removal process

Suint 18.8 Scouring

Dirt 8 Scouring

WET PROCESSING-I (pre-treatment)

Prepared by-

KHURSHEDUL ALAM, Begumganj Textile Engineering College, 2nd

batch.

Email:khurshed_btec2012@yahoo.com.

Oil & fats 11 Scouring

Burrs & others 1.2 Carbonizing

Silk: Silk is an animal fibre. The main ingredient of silk is fibroin (76%). It also contains many

other components which is known as silk impurities.

Impurities Percentage (%) Removal process

Sericin 22 Degumming

Others 2 Scouring