If accurate results are aimed at in the examination of an essential oil according to this table, the specific gravity should be determined by means of a scale sensitive to one one-thousandth gram, and the thermometer should be graduated to the tenth of a degree.
Table Showing the Approximate Density, Boiling and Congealing Points of the most Important Essential Oils Used in Perfumery.
| Essential Oil of | Density. | Boiling Point, Deg. C. | Congealing Point, Deg. C. | Remarks. |
|---|---|---|---|---|
| Absinth | 0·895 | ... | ... | |
| Anise | 0·980 | ... | +10-15 | |
| Bergamot | 0·850-0·890 | 188 | -24 | |
| Bitter almond | 1·040 | 180 | ... | |
| Do., art. (nitrobenzol) | 1·866 | 213 | +3 | |
| Cajuput | 0·880 | ... | ... | |
| Calamus | 0·962 | ... | ... | |
| Camomile | 0·924 | 160-210 | ... | |
| Camphor (Borneo) | ... | 212 | ... | Melts at 198 |
| Camphor (Chinese) | 0·985 | 205 | ... | Melts at 175 |
| Caraway | 0·960 | 195 | ... | |
| Cassia | 1·060 | 252-255 | ... | |
| Cedar wood | ... | 264 | -22 | |
| Cinnamon | 1·030-1·035 | 240 | below -25 | |
| Cinnamon leaf | 1·053 | ... | ... | |
| Clove | 1·034-1·055 | 248 | below 20 | Forms crystals -16 |
| Coriander | 0·871 | 150-200 | ... | |
| Crispmint | 0·978 | ... | ... | |
| Cubeb | 0·880 | ... | ... | |
| Fennel | 0·960-0·980 | ... | +8 | |
| Gaultheria | 1·173 | 224 | ... | |
| Geranium | 0·895 | 216-220 | ... | Forms crystals -16 |
| Hyssop | 0·889 | ... | ... | |
| Juniper | 0·870 | ... | ... | |
| Lavender | 0·870-0·940 | 186-192 | ... | |
| Spike-lavender | ... | 140 | ... | |
| Lemon | 0·850-0·870 | 177-250 | ... | |
| Lemon grass | 0·870-0·898 | 220 | -22 | |
| Limetta | 0·931 | ... | ... | |
| Mace | 0·890-0·950 | ... | ... | |
| Marjoram | 0·890-0·920 | 163 | ... | |
| Melissa | 0·855 | ... | ... | |
| Neroli | 0·889-0·889 | 175 | ... | Forms crystals -16 |
| Nutmeg | 0·880-0·948 | 172 | ... | |
| Nutmeg butter | ... | ... | 31 | |
| Olibanum | ... | 162 | ... | |
| Orange, bitter | 0·830-0·860 | 176 | ... | |
| Orange, sweet | 0·840-0·850 | 176 | ... | |
| Parsley | 1·015 | ... | ... | |
| Patchouly | 0·950-1·012 | 282-294 | ... | |
| Peppermint | 0·902-0·930 | 188-212 | ... | |
| Portugal (orange peel) | 0·840-0·850 | 176 | ... | |
| Rose | 0·832 | 229 | +14-20 | |
| Rosemary | 0·895-0·916 | 185 | ... | |
| Rue | 0·911 | ... | ... | |
| Sage | 0·902 | ... | ... | |
| Santal | 0·950-0·980 | 288 | -22 | |
| Sassafras | 1·082 | ... | ... | |
| Serpyllum | 0·890-0·920 | ... | ... | |
| Star-anise | 0·982 | ... | ... | |
| Thyme | 0·870-0·940 | 170-180 | ... | |
| Vanilla | ... | 150 | 76 | |
| Vetiver | 1·007 | 286 | ... | |
| Wintergreen | 1·180 | 220 | ... | |
| Ylang-ylang | 0·980 | ... | ... | |
| Turpentine | 0·855-0·870 | 160 | ... | |
| Paraffin | 0·870 | ... | ... | Melts at 50-65 |
| Wax | 0·960-0·970 | ... | ... | Melts at 65-70 |
| Spermaceti | 0·943 | ... | ... | Melts at 45-50 |
In buying essential oils, except it be from a house whose reputation is a guaranty of their genuineness, it is to the interest of the perfumer to make a test. He must look for certain substances which are generally used for the sophistication of essential oils. These are: A. Other essential oils; B. Fixed oils; C. Alcohol; D. Paraffin, spermaceti, wax.
A. Adulteration of Essential Oils with Other Essential Oils.
This mode of adulteration, which is frequent, is naturally the one most difficult of demonstration. In the case of cheap oils such as those of caraway, lemon, orange peel, etc., rectified oil of turpentine is almost without exception the adulterant. The methods usually recommended, such as attempting to dissolve out the oil of turpentine by strong alcohol, hoping thus to separate it from the essential oil, are without practical value.
The adulteration can, however, often be demonstrated by rubbing a drop of the suspected oil on a glass plate and testing the odor, provided the olfactory organ is trained. As the above table shows, the oils have different high boiling-points, while oil of turpentine boils at a rather low temperature, hence it evaporates sooner than the others and can be demonstrated by its odor.
The demonstration of an adulteration with an essential oil is most certain by so-called fractional distillation. Some of the oil to be examined (about four to six fluidrachms) is placed in a small retort with condenser and heated to a temperature a few degrees below the boiling-point of the oil in question. If, for instance, oil of bergamot adulterated with oil of turpentine is to be tested, it is heated carefully to nearly 188° C. (370° F.), the boiling-point of the oil of bergamot; the oil of turpentine which boils at 160° C. (320° F.) passes over completely, while the oil of bergamot remains in the retort.
Fractional distillation is also the most reliable way of demonstrating an adulteration with a fixed oil or with paraffin, wax, or spermaceti. An adulteration of oil of lavender with oil of spike-lavender, which is otherwise barely recognizable, is positively shown by this method; even oil of geranium in oil of rose, oil of cassia in oil of cinnamon, etc., may be thus demonstrated.