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Determination of Safrole Content of Essential Oils through Congealing Point Determination
A Cheap and Easy Method Requiring a Minimal Amount of Equipment
Procedure1
Safrole Content | Congealing Point |
100% | +11.0°C |
90% | +7.5°C |
80% | +4.6°C |
70% | +1.7°C |
60% | -1.3°C |
Determine the congealing point of the sassafras oil, and estimate the safrole content from the adjacent table, it will give values of the safrole content with an accuracy of about 2% if the congealing point is above 2°C.
Congealing Points of
Ocotea cymbarum Oil
Samples Varying in
Safrole Content2
Safrole
Content (weight%) |
Congealing
Point |
69.1%
|
2.4°C
|
73.3%
|
3.7°C
|
76%
|
4.4°C
|
79%
|
5.2°C
|
82%
|
6.1°C
|
85%
|
6.9°C
|
86%
|
7.2°C
|
87%
|
7.5°C
|
88%
|
7.8°C
|
89%
|
8.0°C
|
90%
|
8.3°C
|
91%
|
8.6°C
|
92%
|
8.8°C
|
93%
|
9.2°C
|
94%
|
9.4°C
|
95%
|
9.7°C
|
96%
|
10.0°C
|
97%
|
10.3°C
|
98%
|
10.6°C
|
99.5%
|
11.0°C
|
The thermometer used should be calibrated in 0.1°C units and should be accurately standardized. A thermometer covering the range of -5°C to +50°C is satisfactory for most determinations. Before the oil is tested, it should be thoroughly dried with sodium sulfate since the presence of small amounts of water will often materially lower the congealing point. In the case of sassafras oils, it is well to initiate the congelation by the addition of a small piece of solid safrole since sassafras oil can be congealed only with great difficuly if no "seed" is used. For a more exact determination of the congealing point, the test tube containing the supercooled oil may be insulated by means of an air jacket. This is frequently of particular importance when determining congealing points which are much below room temperature, as, for example, the congealing point of euclayptus (sic) oils. Gildemeister and Hoffmann recommend the use of the Beckman apparatus, frequently used for the determination of molecular weights by the lowering of the freezing point. The use of a larger sample (up to 100 mL) may make the congealing point sharper. This method has an accuracy of 0.7% according to the paper2.
Comparative Analyses of Samples
of Oil of Ocotea Cymbarum2
Oil | Congealing Point | Safrole content (from table) | Safrole content (Hg analysis) |
A | 8.7°C | 91.4% | 92.1% |
B | 7.2°C | 86.0% | 85.4% |
C | 8.1°C | 89.3% | 88.6% |
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