Expt No:
MULTI STAGE LEACHING
Date:
AIM:
To study the performance of leaching and to reduce
•
•
•
•
Molarity of Na2CO3 in each stage
Amount of Na2CO3 in overflow in each stage
Total amount of Na2CO3 leached
Percentage of Na2CO3 leached
FORMULA:
• Concentration of Na2CO3 in overflow in each stage =
𝑉𝐻𝐶𝑙 + 𝑁𝐻𝐶𝑙
𝑉𝑠𝑎𝑚𝑝𝑙𝑒
• Amount of Na2CO3 in overflow in each stage( Rn – R0)
= 𝑁 Na2CO3 × 𝑀𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑤𝑒𝑖𝑔ℎ𝑡 × 𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑜𝑣𝑒𝑟𝑓𝑙𝑜𝑤
• Amount of Na2CO3 in overflow in each stage = 𝐸𝑛−1 − 𝑅𝑛
• Operating line equation,
%𝑒𝑛 =
𝐸𝑙𝑎𝑠𝑡 𝑠𝑡𝑎𝑔𝑒 −𝐸0
𝐸0
× 10
THEORY:
Leaching is a liquid-liquid solid operation. The two phases are in intimate
contact. The solute can diffuse from solid to the liquid phase which causes a
separation of components originally in the solid. Leaching in widely used in the
biological & food processing industry such as separation of sugar from sugar
beats with hot water, extraction of oil from peanuts. Leaching of metal from ores.
It is assumed that there is sufficient solvent present so that all the solute in the
entering solid can be dissolved.
TABULATION
Stage
Volume of water
added
(ml)
Volume of Sample
taken
(ml)
OBSERVATION:
Amount of solid taken (B)
=
Amount of Na2CO3 taken (C) =
Total feed
=
A = Solvent used = Water
B = Insoluble = Sand
C = Soluble = Na2CO3
The Normality of HCl given is found to be =
Volume of HCl
consumed
(ml)
PROCEDURE:
• Feed consisting of solids are taken as specified.
• 47.5g of sand perfectly weighed.
• 2.5g of sodium carbonate powder.
• The solids are put together and about 300ml of water is added to the
mixture and stirred well.
• Na2CO3 is allowed to dissolve in the water while the sand settles at the
bottom.
• About 10ml of supernatant overflow is titrated against HCl solution.
• Volume of HCl used for consuming Na2CO3 in the overflow is noted.
• The overflow is discarded and overflow is taken up for subsequent
treatment.
S.NO
Volume of
H2O added
to each
stage (ml)
Normality of
Na2CO3
(N)
MODEL CALCULATION:
Amount of
Na2CO3
leached
(g)
% Leaching
RESULT:
Leaching operation was carried out in overflow where Na 2CO3 and sand
were separated.
Stage
Amount of Na2CO3 leached (g)
% of leaching