Purpose: To use steam distillation to purify heat sensitive, natural products, like essential oils.
Please refer to:
Williamson, Macroscale &Microscale Organic Experiments 4th Ed., pgs.98-109
Table 1.1: Steam distillation
Drop # (every third drop)Temperature (C)Addition of 0.5 mL water
Observations: The residue was cloudy during distillation. This indicated that it was wet. The water was added when the solution appeared to be getting low in volume.
Table 1.2: Recovery of organic material
Object being weighedWeight in grams
Weight of empty, clean test tube6.446 g
Weight of clean test tube with spearmint oil6.635 g
Weight of spearmint oil0.189 g
Table 1.3: IR Spectroscopy
FrequencyCorresponding Functional Group
In this experiment, the process of steam distillation was used to purify a natural product, (the essential oil of spearmint). This phenomenon works because when two immiscible liquids are distilled, the boiling point of the mixture is below the boiling point of the both pure compounds. Since water has a significantly lower boiling point than spearmint, a much greater proportion of water molecules was vaporizing at any time during the distillation. Even though the components of spearmint oil have low vapor pressure, they are volatile enough to vaporize to some extent and a small amount will lifted off with the water molecules. This boiling will occur when the independent internal vapor pressures are equal to 760 torr, which is the external vapor pressure. It is noted that steam distillation, unlike regular distillation, it does not follow Raoult’s Law.
After steam distillation was completed, the essential oil was recovered and a thin layer chromatography was conducted. When this TLC was conducted, there was one spot of pure essential oil and one of the distilled and recovered essential oil. The results indicated that the distilled, recovered oil was pure because it came out as a single spot, level with that of the pure oil. The infrared spectroscopy was performed next. IR spectroscopy is used to identify the functional by stretching and bonding frequencies of bonds. The peaks correspond to the functional groups. Both C-H bonds and C=O bonds were identified through this procedure.
1.In the steam distillation of an essential oil, the observed boiling point is below the boiling point of both the essential oil and of water because they are immiscible liquids. Because of this, the two liquids put forth pressures against the external pressure, and it is known that when the sum of the two partial pressures equal the external pressure, boiling occurs.
2.Cloudy appearance indicates that it is wet.