BACKGROUND
Equilibrium moisture content (EMC) is the amount of water present in the solid, which exerts a vapour pressure equal to the vapour pressure of atmospheres surrounding it.
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When air is continuously passed over the solid containing moisture more than EMC, then solid loses water continuously till EMC is reached. This phenomenon is known as desorption. When air is continuously passed over the solid containing moisture less than EMC, then solid adsorb water continuously till EMC is reached. This phenomenon is known as sorption.1,2
Aim: To determine equilibrium moisture content of starch and bentonite at different humidities and at room temperature.
REQUIREMENTS
| Apparatus: |
| Beakers |
| Weighing balance |
| Desiccators |
| Empty vials |
PROCEDURE
Six desiccators were taken and labelled. 30 ml saturated solutions of potassium acetate, magnesium chloride, magnesium nitrate were prepared in beakers. Saturated solutions were transferred separately into the well of the desiccators.
Weight of each empty bottle (w1g) was recorded. 1 gram quantities of bentonite were transferred into each of 18 vials. Weight of empty bottle and bentonite were noted (w2g) 3 vials of bentonite were placed in each desiccator.
Desiccators were closed with lids firmly using wax. Desiccators were allowed at room temperature undisturbed for one week. After one week, weight of empty bottle and bentonite was noted.
The data was processed as per the table. A graph was plotted by taking relative humidity on x- axis and percent EMC on y- axis. Similarly using starch, steps 5 to 12 were repeated.
Observations and calculations
- Weight of empty bottle = w1 g
- Weight of empty bottle + bentonite = w2 g
- Weight of bentonite = w3 g
- Weight of empty bottle + bentonite after one week of storage = w4 g
- Weight of bentonite after one week of storage = w4 – w1 = w5 g
- Weight of moisture content absorbed during storage = EMC = w5 – w3 = w6 g
- cent moisture absorbed = 100×w6/w3
CONCLUSION
Moisture content of starch and bentonite at different humidities and at room temperature are ___________ .
REFERENCES
- Subrahmanyam CVS, Setty JT, Sarasija S. Laboratory manual of pharmaceutical engineering (Unit operations) C.V.S., Delhi Vallabh Publications.
- Pharmaceutical Engineering by K.Sanbamurty (New Age International, New Delhi)Cooper and Gunn’s Tutorial Pharmacy Edited by S.J.Carter (CBS Publishers, Delhi).
Also read:
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- Study of local anesthetics by Infiltration anaesthesia in guinea pig
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