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ELECTRICAL MEASURING INSTRUMENTS For the detection or measurement of electric current, potential difference, and resistance certain instruments have been devised viz. The galvanometer for the detection of small currents measurements of small currents of the order of micro amperes or mili amperes the voltmeter or potentiometer for the measurement of potential difference (and voltage) between two points of a circuit are the EMF of a source the ammeter for the measurement of large currents the wheatstone bridge the meter Bridge the post office box and the ohmmeter for the measurement of resistance. THE MOVING COIL GALVANOMETER The moving coil galvanometer is a basic electrical instrument it is used for the detection (and Measurement) of small currents. Its underlying principle is the fact that when a current flows in a rectangular coil placed in a magnetic field it experiences a magnetic torque. If it is free to rotate under a controlling torque, it rotates through an angle proportional t...
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HOW TO PREPARE POTASH ALUM? OBJECT : To prepare potash alum (K2SO4,Al2(SO4)3.24H2O) APPARATUS : China dish,beaker,watch glass,funnel,conical flask,glass rod,filter paper,water trough,wire gauze,tripod stand and bunsen burner. CHEMICALS : Solid Aluminium sulphate [Al2(SO4)3.16H2O](7.7 gms) , K2SO4 (2.0 gms), 50 mls of distilled water,few drops of conc H2SO4 EQUATIONS : K2SO4 +Al2 (SO4)3.16H2O + 8H2O --------------> K2SO4.Al2(SO4)3.24H2O THEORY : The term alum was originally used for potassium aluminium sulphate [K2SO4.Al2(SO4)3.24H2O] commonly known as potash alum.The term alum is now used for all double sulphates having general formula R2SO4.M2(SO4)3.24H2O PROCEDURE : Weigh out 7.7 gm of aluminium sulphate and dissolve it in about 30 mls of boiling distilled water.Add few drops of H2SO4 (conc) to make the solution clear.In another beaker dissolve 2.0 g of K2SO4 in 20 mls of distilled water.Mix the two solutions and concentrate the solution to crystallization by heating it in a china...
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HOW TO PREPARE IODOFORM? To prepare Iodoform by the action of iodine on ethyl alcohol in the presence of alkali.\ APPARATUS: Two 100 mls beakers ( one for ethanol and other NaOH solution),glass rod,filter paper,funnel,watch glass . CHEMICALS: Ethanol (ethyl alcohol absolute) 10 mls 10% NaOH solution (20 mls) powdered iodine (2 gms) distilled water. THEORY: The reaction of halogens with alcohol or carbonyl compounds (acetaldehyde CH3 - CHO or methyl ketones CH3 - C  R) in the presence of alkali NaOH to form haloform (CHX3) is called haloform reaction.If the halogen is iodine the the formation of iodoform will take place and the reaction is called iodoform reaction. In the first reaction,ethyl alcohol is oxidized to acetalhyde.In the next step acetalhyde reacts with iodine to give tri-iodo acetaldehyde or iodal which on reaction with NaOH gives iodoform. EQUATION:  C2H5OH + 4I2 + 6NaOH ------------> CHI3 + HCOONa +5NaI + 5H2O PROCEDURE: Take 2gms of powdered iodine in a beake...
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CHLORINE ELECTROLYSIS METHOD: Chlorine is manufactured by the electrolysis of aqueous solutions of sodium chloride.For this purpose two cells are used which are described below: (a) NELSON'S CELL: This cell consists of U-shaped perforated steel vessel which acts as cathode and carbon rod as anode.This U-tube is separated from anode by asbestos layer on the inner wall of the U-Tube as shown in figure The U-tube is filled by aqueous solution of sodium chloride.On passing the electric current,chlorine is obtained at anode reaction: (i) Ionization NaCl ---------> Na + Cl (ii) Reaction at anode 2Cl - 2e ----------> Cl2   (b) CASTNER-KELLNER'S CELL: This cell has a Cathode consisting of layer of mercury at the bottom of cell which flows from right to left.Saturated solution of sodium chloride also flows slowly through the cell in same direction as the mercury.The anode rods are of graphite which dip into the solution of sodium chloride. On electrolysis chlorine is liberated at ...
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ATOMIC HYDROGEN Ordinary hydrogen exists as diatomic molecules (H2). Therefore it is also called as molecular hydrogen.The two atoms in a molecule of hydrogen are held together by shared pair of electron known as covalent bond having very high bond energy (104 cal. mol-1.The molecules are very stable and dissociate into atoms only under extreme conditions.The product obtained as a result of dissociation of molecular hydrogen is known as atomic hydrogen. These atoms have very short life and quickly combine together to form molecules again. PREPARATION OF ATOMIC HYDROGEN:- Atomic hydrogen is prepared by thermal decomposition of ordinary hydrogen or by electrical dissociation under reduced pressure. H2 + 104K.cal -------------> 2H H2 ------------------------------>2H  PROPERTIES OF ATOMIC HYDROGEN:-  Atomic hydrogen is much more reactive than molecular hydrogen.Expected reactions of molecular hydrogen are only those in which more than 104K.cal per mole are evolved per two g...
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REFINING OF PETROLEUM  Petroleum is refined by distillation.Crude oil is carried by pipes to a fractionating column and heated to above 400 C.A number of products are obtained at different temperatures and condensed. More than 500 compounds have been formed in petroleum distillate boiling below 200 C.Gasoline or petrol is a mixture of hecane (C6H14) and heptane (C7H16) and Heptane (C7H16) Since the demand of gasoline is increasing due to to its increased use a fuel for automobiles, airplanes etc.The cracking is employed to obtain increased quantities of petrol from crude oil. REFORMING OF PETROLEUM :- Knocking is a sharp metallic sound produced in the internal combustion engine.Its a cause is gasoline of low octane number.T he octane number of gasoline is improved by reforming,a process some what similar to cracking,which again brings about the arrangements of straight chain alkanes into branched chain alkanes.If the petrol used is of such quality that its vapour mixed with air can...
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NATURAL SOURCES OF ORGANIC COMPOUND  The mineral sources of organic compound are coal,natural gas and petroleum.Plants are also among natural sources of important organic compounds. COAL :- The bituminous or soft coal is a very important source of organic compounds.This when subjected to destructive distillation, products of industrial importance are obtained.  FRACTIONAL DISTILLATION OF COAL-TAR:- When coal is destructively distilled four principal fractions are obtained, viz: coal gas , coal tar ,coke and ammonical liquors. Of these coal gas which consists mainly of methane and hydrogen is used as a fuel,while coke a form of carbon,is used in the manufacture of iron and steel industry.The composition of coal tar varies depending on the nature of the coal.However, coal is composed of various aromatic hydrocarbons. These components are separated by fractional distillation of coal tar.It has been calculated that 100 Kg of coal tar yield 1-2 Kg of benzene. NATURAL GAS :- Natural...
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LEAD PIGMENT Lead forms various types of pigments which are used to give the proper color to paints etc.Some of them are described below: White Lead pigment Red Lead Pigment Chrome Yellow Pigment Chrome Red Pigment Turner's Yellow Pigment (i) White Lead Pigment : It is a basic lead carbonate and has approximately composition as [ 2PbCO3.Pb(OH)2] or [Pb3.(CO3)2] Preparation : Chamber Process or Duch Process : When a mixture of the vapours of acetic acid and steam is passed into the chambers containing lead sheets (buckets) about 2-3 days,until the corrosion of lead is complete.By passing the mixture of CO2 and vapours of acetic acid through this corroded lead for about 3-4 weeks,the White Lead is formed on the surface of lead sheets.This product is then scratched,dried and packed. 2Pb +2CH3COOH + 2H20 ---------> [Pb(OH)2.Pb(CH3COO)2] + 2H2 3[Pb(OH).Pb(CH3COO)2] + 2H2O + 2CO2 -------------> 2[2PbCO3.Pb(OH)2] + 6CH3COOH A better "White Lead" is obtained by passing CO2 ...
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