Paints are stable mechanical mixtures of one or more pigments. The main function of the pigments is to impart the desired colour and to protect the paint film from penetrating radiation, such as U.V. rays.

`=>` Plasticisers are added during the manufacturing of paint in order to provide elasticity to the film and minimise its cracking.

`=>` Chromium oxide gives green colour to the paint.

`=>` Aluminium paints are heat resistant but cannot be used for water pipe. Lithopene `[BaSO_4 + ZnS]` is a substitute of white lead.

`=>` Titanium dioxide (Titanox) is extensively used in the manufacture of paints and pigments.

`=>` Cadmium lithopones (cadmopones) `(Cds + BaSO_4)` is used as yellow pigment.

`text(Constituents of Paints) : `

(i) Pigments : These substances impart colour to another substance. These have a definite colour.

(ii) Solvents : Normally some oil like terpentine oil is used as a solvent.

(iii) Driers : These are used to dry the paints. These are cobalt, lead manganese, rosinates compounds e.g. `MnO , CaO ` etc.

(iv) Thinners : These are used for reducing the viscosity of paints. These increase the volume of paint. e.g. alcohol, kerosene oil etc.

(v) Fillers or extenders : The substances are used to increase the concentration of pigment or paint. These are low gravity material

e.g. `BaSO_4 * ( Cu SO_4) * 2H_2O`

Commonly Used Pigments

Pigment	Colour	Formula
White lead	White	`2[Pb(OH)_2*2PbCO_3]`
Chrome yellow	Yellow	`PbCrO_4`
Chrome red	Red	`PbCrO_4 * PbO`
Basic lead sulphate	White	`2PbSO_4 * PbO`
Red lead or sindhur	Red	`Pb_3O_4`
Litho pone	White	`BaSO_4+ZnS`
Malachite	Green	`Cu (OH)_2 * CuCO_3`
Azurite	Green	`Cu(OH)_2 * 2CuCO_3`
Thenard	Blue	`CoO*Al_2O_3`
Smelt	Blue	`K_2O*CoO*3SiO_2`

Safety Matches :

The credit for developing friction matches that are presently still in use has been attributed to English chemist, John Walker, in 1826. He made matches involving a mixture of potassium chlorate, antimony (III) sulfide, gum and starch, which ignited when struck on sandpaper. These matches were somewhat unreliable in their performance. These days the head of the safety match contains only antimony trisulphide (`Sb_2S_3`) and potassium chbrate (`KClO_3` ). The rubbing surface has powdered glass and a little red phosphorus (which is less dangerous). When the match is struck against the rubbing surface, some red phosphorus get converted into white phosphorus. This immediately reacts with potassium chlorate in the matchstick head to produce enough heat to ignite antimony trisulphide and start the combustion.

Gun Powder : Gunpowcter was the only known chemical explosive till mid of the 19th century.

Gunpowder is a mixture of three different components : Potassium nitrate, `KNO_3` (also called saltpetre) (75% by weight), Charcoal (15% by weight), and sulphur (10% by weight).

`=>` The granules of modern gun powder (black powder) are coated with graphite because graphite reduces the moisture absorbing capacity of the powder. Graphite also prevents the build-up of electrostatic charge to prevent accidental ignition.

`=>` It is first chemical explosive and during explosion `N_2` and `CO_2` are evolved in the ratio of `1 : 3`.

Note :

`=>` Water is the most common fire extinguisher but it is not suitable for fires involving oil, petrol and electrical equipment. In
these cases `CO_2` is the best extinguisher.

`=>` Dry powder of chemical like sodium bicarbonate or potassium bicarbonate are used is a fire extinguisher. Sodium bicarbonate
and sulphuric acid are used in soda acid fire extinguisher and aluminium sulphate in foam fire extinguisher.

Plastics : When unsaturated hydrocarbons e.g. ethylene, propylene, butylene etc. undergo polymerisation under specific conditions then higher polymer plastic is obtained. These are of two types :

(i) Thermoplastics : are linear in structure can be soften on heating and becomes harden on cooling. This character is maintained through out its existence. e.g. polythene, polystyrene, polyvinylchloride, teflon.

(ii) Thermosetting plastics : undergo permanent change on heating due to excessive cross linking and cannot be remoulded and reused, e.g. bakelite, melmac.

Polymers along with their Monomers :

Polymer	Monomer
Polyethylene	Ethene
Polystyrene	Styrene
Polyvinylchloride (PVC)	Vinylchloride
Polytetrafluoroethylene [PTFE/Teflon]	Tetrafluoroethene
Bakelite	Formaldehyde + Phenol
Urea-formaldehyde resin	Urea + Formaldehyde
Mel mac	Melamine + Formaldehyde

Fibres : The solid substance which has thin long chain structure is called fibre. Cotton, jute, silk, wool are natural fibres whereas rayon, nylon, polyster are synthetic fibres. Fibres possess strong intermolecular forces like hydrogen bonding e.g. nylon -6,6, dacron, orion.

`=>` Rayon (acetate rayon and viscose rayon) is called artificial silk.

Synthetic Fibres with their Monomers

Fibres	Monomers	Uses
Nylon-66	Adipic acid +hexamethylene diamine	In making bristles for brushes parachutes, as a substitute for metal in bearings.
Nylon-6 or pinion	Caprolactum	In making fibres, plastics tyre cords and ropes
Terylene or Dacron	Ethylene glycol and terephthalic acid	For making wash and wear fabrics. tyre cords, safety belts, tents etc.
Polyurethanes	Toluene diisocyanate + ethylene glycol	For making washable and long lasting mattresses, cushions

`=>` Orion is obtained by polymerisation of vinyl cyanide.

`=>` Carbon fibres are made from long chains of carbon atoms in which corrosion does not take place. These are used in making parts of space vehicles and sports items.

`text(Natural Rubber) :`

`=>` Natural rubber is a linear polymer of isoprene and it is also called cis-1, 4 poly isoprene. It is an elastomer which is insoluble in water, dilute acids and alkalies.

`=>` Natural rubber absorbs a large amount of water and possess low tensile strength.

`=>` The process of heating a natural rubber with 5%, sulphur in the presence of `ZnO` at `373K` in order to improve their properties is called vulcanisation of rubber. Carbon black is added to vulcanised rubber for hardening of tyres.

A chemical fertilizer is defined as any inorganic material of wholly or partially synthetic origin that is added to the soil to sustain plant growth. These are added to the soil during sowing season to avoid starvation of the plants to ensure healthy crops. About 16 elements are needed for the healthy growth of a plant. Among these, nitrogen, phosphorus and potassium are the major elements needed in large amounts.


Types of Fertilizers : There are two types of fertilizers.

1. Chemical Fertilizers/Synthetic Fertilizer : These are man-made and nutrient specific fertilizers that are added to the soil according to their need. These fertilizers are also called artificial fertilizers.
Chemical fertilizers mainly of three types:

(i) Nitrogeneous Fertilizers : `NH_3` is the feed stock of all nitrogenous fertilizers such as anhydrous ammonium nitrate (`NH_4NO_3`) and urea (`CO(NH_2)_2)`. `NH_3` is obtained by Born Haber process.

Some of them are as follows

(a) Urea `(NH_2CONH_2) :`

`=>` Urea is the best nitrogeneous fertilizer having 47% nitrogen by weight.

Note : Percentage of an element in a compound `= (text(Total mass of an element ) xx 100)/text(Molar mass of compound)`

N% by weight = `text(Total mass of N)/text(Total mass of urea ) xx100`

`N % = ( 2xx14)/(60) xx 100 = 46.67 % approx 47 %`

`=>` Urea is a white crystalline solid (melting point `133^0 C`). It is soluble in water but insoluble in ether.

`=>` On hydrolysis, urea gives `CO_2` and `NH_3`.

`=>` Urea is not as stable as other nitrogeneous fertilizers and decomposes even at lower temperature in humid atmosphere.

(b) Ammonium Sulphate `[NH_4]_2 * SO_4` :

`=>` It is prepared by absorbing ammonia in sulphuric acid.

`2NH_3+H_2SO_4 → undersettext(Sindri fertilizer) ((NH_4)_2SO_4)`

`=>` It is a white crystalline solid soluble in water. It contains `21 %` nitrogen.

`=>` Hydrolysis of ammonium sulphate produces `H_2SO_4`.

`(NH_4)_2SO_4+2H_2O → 2NH_3+H_2SO_4+2H_2O`

Therefore, its repeated use makes the soil acidic and unfit for germination of seeds. To neutralise it lime is added to acidic soil. Hence, ammonium sulphate should not be used very frequently.

(c) Calcium Cyanamide or Nitrolim `(CaCN_2)` :

`=>` It is prepared by passing a stream of nitrogen gas over hot `CaC_2` at `100^0 C`, when nitrolim is obtained.

`CaC_2+N_2 overset(1100^0 C)→ undersettext(Calcium cyanamide) (CaCN_2)+C`

`=>` Calcium Cyanamide is a low acting manure having 19% nitrogen by weight.

`=>` It is black in colour. lt contains 19% nitrogen. It is slowly hydrolysis by the soil moisture to ammonia and calcium carbonate.

`CaCN_2+3H_2O → CaCO_3+2NH_3`

(d) Calcium Ammonium Nitrate : `[Ca(NO_3)_2 * NH_4NO_3]`

`=>` It is prepared by treating limestone with excess of nitric acid. The resulting solution is neutralised by passing ammonia gas. From the solution CAN is crystallised out.

`=>` It contains nitrogen in readily palatable forms for plants.

(ii) Phosphatic Fertilizers :

`=>` These fertilizers mainly supply phosphorus. Phosphorus is needed for stimulating growth and enables the plants to resist the attack of diseases and also helps in the ripening of fruits.

`=>` These fertilizers supply phosphorus whose content is expressed as `P_2O_5`.

Some of them are as follows

(a) Calcium Superphoshate or Superphosphate of Lime `[ Ca (H_2Po_4)_2+2CaSO_4 * 2H_2O ]`

`=>` The water soluble component of superphosphate of lime is calcium dihydrogenphosphate `[Ca(H_2PO_4)_2]`.

`=>` It contains `15 - 16 %` of `P_2 O_5`.

(b) Triple Superphosphate `[Ca(H_2PO_4)_2]` :

`=>` It is soluble in water.

`=>` Triple superphosphate usually contain `43 - 46 %` of `P_2O_5`.

`=>` It is prepared by the action of `54 %` phosphoric acid on calcium phosphate.

(c) Thomas Slag `Ca_3 (PO_4)_2 * (CaSiO_3)`

`=>` It is soluble in water in the presence of salt and carbon dioxide .

`=>` Phosphatic slag gives a steady supply of phosphatic acid for the plant growth . It has `14 - 18 %` of `P_2O_5`.

(iii) Potash Fertilizers :

`=>` lt gives structural growth to the plant . These are mainly required for the development of healthy roots and also aids ripening of cereals and fruits.

`=>` Potassium sulphate has been found to be more stable for tobaco plants. It is because the ash of tobaco grown by it has a high melting point. Tabaco needed for making cigarettes should have high melting point.

`=>` These fertilizers are available in nature as soluble salts like `KCl , K_2CO_3 , KNO_3` and `K_2SO_4` . These supply mainly potassium to the plnts e.g. muriate of potash `(KCl)` , potassium nitrate, `(KNO_3)`, potassium sulphate `(K_2SO_4)`.

`=>` Potash fertilizers evaluated as `K_2O`.

Mixed Fertilizers or NPK Fertilizers :

`=>` These contain more them one fertilizing ingredient.

`=>` It is better to use these fertilizers as these supplies all the essential nutrient to the plants. e.g. nitrophosphate ammonium phosphate.

`=>` NPK, also called as Kisan Khad or Kisan Urea. It contains nitrogen, phosphorus and potassium.

Harmful Effects of Chemical Fertilizers :

`=>` These are lost readily when applied in field.

`=>` These are expensive and their production releases pollutants and cause pollution of soil, air and water.

2. Natural Fertilizers : Natural fertilizers are of biological origin. These can be classified as

Manure :

`=>` It contains large quantities of organic substances formed by the decomposition of animal excreta and plant waste

`=>` It supplies small quantities of nutrients to the soil.

`=>` Manure includes farmyard manure, compost and green manure.

`=>` The bulk of organic matter in manure helps in improving soil structure.

Green Manure :

`=>` Some plants like guar or sunhemp are grown and mulched by ploughing them into the soil. These plants turn into green manure.

`=>` Green manure helps in enriching the soil in nitrogen and phosphorus.

Biofertilizer :

`=>` Biofertilizers : are organism which can bring soil nutrient enrichment. The main sources of biofertilizers are bacteria, cyanobacteria and fungi.

`=>` Mycorrhiza is a symbiotic association of certain fungi with roots of higher plants. It increase water and nutrient intake by plants and increases growth and yield of plants.

`=>` Rhizobium and blue green algae are two important biofertilizers.

`=>` Biofertilizer and green manures do not pollute the soil.

`=>` Field with leguminous plants is rich with nitrogen element.

`=>` Legumes revive soil fertility.

Reagents :

• Fehling solution :`CuSO_4`+ Sodium potassium tartrate (Rochelle salt)+`NaOH`.
• Tollen's reagent :`AgNO_3` solution + `NaOH +NH_4OH`
• Sodalime `: Ca (OH)_2+NaOH`
• Lithopone ` : BaSO_4+Zns`
• Nessler's reagent `: K_2{HgI_4]`
• Milk of magnesia `:` Suspension of `Mg(OH)_2` in water .

Processes :

• Nelson cell `: NaOH`
• Mac Arthur Forest process `: Ag` (cyanide process)
• Mond process `: Ni`
• Berkeland Eyde process `: NO , HNO_3`
• Lead chamber process `: H_2SO_4`.

• Magnesite `: MgCO_3`
• Kieserite `: MgSO_4 ·H_2O`
• Epsomite `: MgSO_4 ·7H_2O`
• Sorel's cement `: MgCI_2 ·5MgO·xH_2O`
• Limestone, marble, chalk `: CaCO_3`
• Gypsum `: CaSO_4 *2H_2O`
• Plaster of Paris `: CaSO_4 · 1/2 H_2O`
• Quick lime `: CaO`
• Slaked lime `: Ca (OH)_2`
• Carnallite `: KCl MgCl_2 · 6H_2O`
• Permutit (Zeolite) `: Na_2Al_2SiO_4 ·xH_2O`
• Soda ash : anhy. `Na_2CO_3`
• Washing soda `: Na_2CO_3 ·10H_2O`
• Crystal carbonate `: Na_2CO_3 ·H_2O`
• Marshall's acid `: H_2S_2O_8`
• Borazine (Inorganic benzene) `: B_3N_3H_6`
• Blue vitriol `: CuSO_4 ·5H_2O`
• Horn silver `: AgCl`
• Philosophere wool `: ZnO`
• Corundum `: Al_2O_3`
• Bauxite `: Al_2O_3 · 2H_2O`
• Carborundum `: SiC`
• Calomel excess `: Hg_2Cl_2`
• Freon `: CF_2CI_2`
• Oil of vitriol : conc. `H_2SO_4`
• Refrigerant: `: NH_3, CF_2CI_2, CO_2` etc.