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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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MANUFACTURE OF SODIUM BICARBONATE AND SODIUM CARBONATE BY SOLVAY-PROCESS :
INTRODUCTION : 

Solvay process was introduced by Belgian engineer Ernest Solvay (1861) for manufacture of sodium bicarbonate (baking soda) and sodium carbonate (washing soda). This process is also known as "Ammonia soda process" due to use of ammonia.

DETAILS OF THE SOLVAY PROCESS :

Solvay process involves the following steps:

1. AMMONIATION :

Concentrated brine (sodium chloride) solution is prepared by dissolving NaCl in water.Then the brine is purified by lime-soda treatment to precipitate calcium and Magnesium as carbonate which settle down.Then the brine is pumped into a tower in which strream of ammonia gas is passed through it, the brine saturated with ammonia is called "Ammonical brine" in which CO2 is more soluble than ordinary brine.

2. CARBONATION :

Carbonation involves combination of CO2 with ammonical brine. For this purpose CO2 is prepared in a skin by heating lime-stone.

CaCO3 -----> CaO + CO2 (Quick Lime) 

"CO2 is sent to carbonation tower where it comes in contact with ammonical brine"

Carbonation tower is also known as "Solvay Process" which is filled with dome-shaped perforated plates.Ammonical brine is allowed to trickle down the tower while CO2 is forced up.The arrangement in the tower makes the better contact between ascending gas and descending liquid.

REACTION :

In solvay process,following reactions take place.
NH3 and CO2 react to ammonium bicarbonate.

2NH3 + CO2 +H2O -----> (NH4)2.CO2

(NH4)2.CO3+CO2+H2O -----> 2NH4HCO3

NH4HCO3 further reacts with NaCl as follows.

NH4HCO3 + NaCl -----> NaHCO3 + NH4Cl

Sodium bicarbonate is slightly soluble in H2O and separates out as white precipitate.During the reaction the temperature is kept at 30-40 C temperature but near the completion, the temperature is reduced is 15 C to ensure maximum separation  of NaHCO3.

FILTRATION :

Sodium Bicarbonate is filtered, washed with water dried and heated in an oven to get anhydrous sodium carbonate.

2NaHCO3 -------> Na2CO3 + H2O + CO2

2Na2CO3 +10H2O ------> Na2CO3.10H2O

RECOVERY OF AMMONIA :

Filtrate obtained as results of filtration of NaHCO3 contains NH4Cl which sent to ammonia recovery tower Lime obtained form lime kiln is added to it to produce NH3 for further use.

CaO + 2NH4Cl -----> CaCl2 + 2NH3 + H2O

USES :

1. It is used in the manufacture of glass, water glass enamels, soap, detergents and papers.
2. It is used as washing soda in laundry.
3. It is used in textile industry and petroleum refinery.
4. It is used for removing permanent hardness of water.












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