The Effect of Concentration on the Rate of Evaporation

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BACKGROUND

Evaporation is a process of vaporizing large quantities of volatile liquid to get a concentrated product. The rate of evaporation depends on several factors such as temperature such as temperature, viscosity, concentration of the slurry,vapour pressure, surface area,and time of evaporation, films, and deposits.¹ The higher the temp, the greater will be the rate of evaporation. The greater the surface area of the liquid, the greater will be the evaporation. If the time of exposer is longer, greater will be the evaporation. Films and deposits formed during evaporation reduce the evaporation.² Higher the viscosity of the slurry, the lower the rate of evaporation. Higher the conc. Of dissolved solid, the lower the rate of evaporation.^3,4

Aim: To study the effect of concentration on the rate of evaporation.

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REQUIREMENTS

Apparatus:     Breaker, 50ml of Glycerin

Breaker, 100ml of purified water

Breaker, 250ml of Sodium chloride solution

Water- bath

Balance

Weight box

Measuring scale

Measuring cylinder

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PROCEDURE

2, 4, 6 & 8 % w/v Solution of NaCl were prepared by dissolving 1, 2, 3, &4 g of NaCl in 50 ml of water in beakers. The beakers contain NaCl solution are weighted (w3 g) weighted are recorded in column 4 of Table-3. All the breakers are heated in water bath at cont. temperature (70 ^{0 c}) for 30 minute. All the beakers were weighted again after heating (w6 g). Weights are located in column 5 of Table- 3. The difference between the weights was determined. The difference reflects the amount of water evaporated during 30 minutes. Rate of evaporation was calculated. A graph is plotted by taking rate of evaporation on y-axis and concentration x-axis.

Observation Table

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CONCLUSION

With increase in concentration of sodium chloride solution, rate of evaporation ________

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REFERENCES

1. Subrahmanyam CVS, Setty JT, Suresh S. Laboratory manual of pharmaceutical engineering (Unit operations). Delhi Vallabh Publications.
   
2. Pharmaceutical Engineering by K.Sanbamurty (New Age International, New Delhi)
   
3. Cooper and Gunn’s Tutorial Pharmacy Edited by S.J.Carter (CBS Publishers, Delhi)
   
4. Pharmaceutical Dosage forms by Aulton. (Churchill Livingstone, Edinburg)
   
5. Chemical Engineering by Badger and Banchero (Mc Graw Hill, New Delhi)