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BACKGROUND
Humidity is defined as the ratio of mass of water present in the air to the mass of dry air. Relative humidity is defined as the ratio of actual humidity to the saturation humidity at a temperature. Dry bulb temperature: it is the temperature of the moisture when it is measured at rest which is not affected by the moisture content of the air or by radiation.
Wet bulb temperature: it is the dynamic equilibrium temperature attain by a water surface when exposed to air under adiabatic conditions.1,2
Sling psychrometer
Sling psychrometer consists of two similar thermometer that are fixed to a metal frame .the bulb of one thermometer is kept open to the ambient conditions. This thermometer gives dry bulb temperature. The bulb of second thermometer is kept moist by a wet cotton wick immersed in a water reservoir. This thermometer gives wet bulb temperature. When the sling psychrometer is kept for a while the wet bulb thermometer reaches a minimum and remains constant. The temperatures of two thermometer were noted.3
Psychrometric chart
Psychrometric is a term used for determination of the vapour concentration and carrying capacity of the gas.
The various parameters of Psychrometric chart:
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Humidity Vs temperature
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Humid heat Vs Humidity
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Specific volume Vs Temperature
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Adiabatic cooling lines
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Saturation humidity curve
Saturation humidity is absolute humidity at which the partial pressure of water vapour in the air is equal to the vapour pressure of free water at the same temperature4,5.
Sling psychometer
gives wet bulb and dry bulb temperature .the wet bulb temperature is a function of temperature and humidity of air used for evaporation. The difference between wet bulb and dry bulb temperature are used for calculating the % relative humidity and humidity of air.
% Relative humidity = Humidity of air / Humidity of saturated air * 100
The intersection point is identified at which the saturated curve crosses the wet bulb temperature .From this point the horizontal line towards the Y-axis (Humidity scale) is drown and humidity values are noted.
Aim: To determine the humidity and relative humidity of the ambient environment using psychomotor.
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REQUIREMENTS
Apparatus: Sling Psychrometer containing wet bulb and dry bulb thermometers.
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PROCEDURE
The Sling Psychrometer was taken and verified for the dry bulb thermometer which was exposed to open air.
The wet bulb thermometer was verified for its cloth sack dipping in the water present in the plastic container. The dry bulb and wet bulb temperature were noted.
The humidity and relative humidity were determined by using humidity charts.
Observations and calculations
| Temperature | Humidity | Relative Humidity |
| Dry bulb temperature | ||
| Wet bulb temperature |
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CONCLUSION
The relative humidity was found to be ________________
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REFERENCES
- Subrahmanyam CVS, Setty JT, Sarasija S. Laboratory manual of pharmaceutical engineering ( Unit operations), 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)
- Pharmaceutical Dosage forms by Aulton.(Churchill Livingstone, Edinburg)
- Chemical Engineering by Badger and Banchero (Mc Graw Hill, New Delhi)
