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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 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 beaker and add 10mls of ethyl alcohol,dissolve the contents by constant by constant stirring with the help of a glass rod until violet color if iodine disappears and reddish brown solution is obtained.Now to this solution add freshly prepared 10% NaOH solution in excess (about 20%). Well mix the contents, when iodoform will begin to separate almost immediately.Allow the mixture to stand at room temperature for dew minutes and filter it.Wash iodoform crystals with cold distilled water dry the yellow crystals of iodoform.

In order the to get pure iodoform, dissolve the crude iodoform in least possible quantity of hot ethyl alcohol.Filter to remove the impurities and add water to the filterate until iodoform is completely precipitated.Filter it and dry.

RESULT:

The yellow crystals of iodoform are obtained.

Hope after reading the article,you understand

How to prepare iodoform ?
What is equation of idoform?
What is the chemical formula of iodoform?

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