July 20, 2024

Determination of humidity air wet and dry bulb temperatures Dew point method

Determination of humidity air wet and dry bulb temperatures Dew point method

Pharmaceutical Engineering Practical Lab Manual PDF Download


To determine the humidity of the air using wet and dry bulb temperatures and the dew point method.


Humidity refers to the amount of moisture present in the air. This experiment employs the wet and dry bulb temperatures to determine humidity. The wet bulb temperature is measured using a thermometer with its bulb covered in a wet cloth exposed to moving air, which causes evaporation and lowers the temperature. The dry bulb temperature is the regular air temperature. The difference between these temperatures, along with the atmospheric pressure, helps calculate the relative humidity and find the dew point.


  1. Dry Bulb Thermometer
  2. Wet Bulb Thermometer
  3. Whirling Hygrometer
  4. Chart for Calculations
  5. Calculation Sheet


  1. Setup Preparation:
    • Calibrate the thermometers.
    • Prepare the whirling hygrometer.
  2. Measurement:
    • Note the dry bulb temperature (Tdb) using the dry bulb thermometer.
    • Wet the cloth covering the wet bulb thermometer and start rotating it.
    • Wait for the temperature to stabilize and note down the wet bulb temperature (Twb).
    • Record atmospheric pressure.
  3. Calculations:
    • Use the chart and the readings to find the difference between the dry and wet bulb temperatures.
    • Determine the relative humidity using the difference and atmospheric pressure.
    • Calculate the dew point using the readings and a suitable chart or formula.


  • Dry Bulb Temperature (Tdb): [Recorded Value]
  • Wet Bulb Temperature (Twb): [Recorded Value]
  • Atmospheric Pressure: [Recorded Value]
  • Difference between Tdb and Twb: [Calculated Value]
  • Relative Humidity: [Calculated Value]
  • Dew Point: [Calculated Value]


After the calculations, you’ll obtain the relative humidity and the dew point temperature. This experiment helps students understand the practical aspects of measuring humidity and its relevance in pharmaceutical settings.

Pharm Engg Chapterwise MCQ: UNIT-I MCQ * Flow of fluids * Size reduction * Size separation UNIT-II MCQ *Heat transfer *Distillation *Evaporation UNIT-III MCQ *Drying * Mixing UNIT-IV MCQ * Filtration * Centrifugation * UNIT-V MCQ Materials of construction * Corrosion

Pharmaceutical Engineering Practical Lab Manual PDF Download

I. Determination of radiation constant of brass, iron, unpainted and painted glass.
II. Steam distillation – To calculate the efficiency of steam distillation.
III. To determine the overall heat transfer coefficient by the heat exchanger.
IV. Construction of drying curves (for calcium carbonate and starch).
V. Determination of moisture content and loss on drying.
VI. Determination of humidity of the air – i) From wet and dry bulb temperatures –use of Dew point method.
VII. Description of Construction working and application of Pharmaceutical Machinery such as rotary tablet machine, fluidized bed coater, fluid energy mill, dehumidifier.
VIII. Size analysis by sieving – To evaluate size distribution of tablet granulations – Construction of various size frequency curves including arithmetic and logarithmic probability plots.
IX. Size reduction: To verify the laws of size reduction using a ball mill and determining Kicks, Rittinger’s, Bond’s coefficients, power requirement and critical speed of Ball Mill.
X. Demonstration of colloid mill, planetary mixer, fluidized bed dryer, freeze dryer and such other major equipment.
XI. Factors affecting Rate of Filtration and Evaporation (Surface area, Concentration and Thickness/ viscosity)
XII. To study the effect of time on the Rate of Crystallization.
XIII. To calculate the uniformity Index for a given sample by using Double Cone Blender.

Second Year B Pharm Notes, Syllabus, Books, PDF Subjectwise/Topicwise

S Y B Pharm Sem IIIS Y B Pharm Sem IV
BP301T Pharmaceutical Organic Chemistry II TheoryBP401T Pharmaceutical Organic Chemistry III Theory
BP302T Physical Pharmaceutics I TheoryBP402T Medicinal Chemistry I Theory
BP303T Pharmaceutical Microbiology TheoBP403T Physical Pharmaceutics II Theory
BP304T Pharmaceutical Engineering TheoryBP404T Pharmacology I Theory
BP305P Pharmaceutical Organic Chemistry II PracticalBP405T Pharmacognosy I Theory
BP306P Physical Pharmaceutics I PracticalBP406P Medicinal Chemistry I Practical
BP307P Pharmaceutical Microbiology PracticalBP407P Physical Pharmaceutics II Practical
BP308P Pharmaceutical Engineering PracticalBP408P Pharmacology I Practical
BP409P Pharmacognosy I Practical

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