A Practical Treatise on the Manufacture of Perfumery. C. Deite
after settling, the more distinct and beautiful the color of the oil and of the precipitate appears. For the establishment and certain recognition of very small quantities of oil of turpentine in oxygenated oils, it is best to first add very little of the nitroprusside of copper to the oil to be tested, and a larger quantity only after being convinced either of the purity or adulteration of the oil. This is done to be able, on the one hand, better to judge the reaction, if the oil is pure, and, on the other, if it is adulterated, to establish such adulteration with certainty and to approximately estimate the quantity of oil of turpentine present. The less nitroprusside of copper is used, the better small quantities of oil of turpentine can be detected.
Nearly all volatile oils free from oxygen show the same behavior towards nitroprusside of copper; they decompose it, which is not the case with oxygenated oils. The behavior of the latter is shown in the following table:—
| Name of the oil | Color of the oil | Proportion of nitroprusside of copper to oil | Color of the oil after the experiment | Color of the Precipitate |
|---|---|---|---|---|
| Caraway | clear as water and colorless | 1:1000 parts | slightly yellowish | dirty gray. |
| Fennel | pale yellowish | 1:1000 " | brownish-yellow | black. |
| Dill | pale reddish-yellow | 1:1000 " | becomes first colorless, then yellowish | " |
| Anise-seed | pale yellow | 1:1000 " | yellow | " |
| Camomile (green) | yellowish | 1:1000 " | brownish-yellow | ash-gray. |
| Lavender | pale yellow | 1:1000 " | wine-yellow | slate-gray. |
| " | " | 1: 100 " | brown-yellow | " |
| Mint(curly) | colorless | 1:1000 " | wine-yellow | first gray, then black. |
| Peppermint | " | 1:1000 " | yellowish | black. |
| " | " | 1: 100 " | brownish-yellow | " |
| Balm | yellow | 1:1000 " | dark wine-yellow | " |
| Marjoram | colorless | 1:1000 " | yellowish | " |
| " | " | 1: 100 " | brown-yellow | " |
| Sage | slightly yellowish | 1:1000 " | wine-yellow | dark green. |
| " | " | 1: 100 " | brown-yellow | dark green, then nearly black. |
| Thyme(field) | " | 1:1000 " | brownish-yellow | slate-gray. |
| " | " | 1: 100 " | darkbrown-yellow | nearly black. |
| Wormwood | yellow-brown | 1:1000 " | dark brown | black. |
| Tansy | pale yellow | 1:1000 " | red-brown | dirty brown. |
| Milfoil | dark azure-blue | 1:1000 " | first pale blue, then dark green | gray-brown. |
| Cajeput | colorless | 1:1000 " | brownish-yellow | black. |
| Clove | slightly yellowish | 1:2000 " | rose-red and clear | slate-gray. |
| " | " | 1:1000 " | violet-red and clear | " |
| " | " | 1: 500 " | cherry-red and opaque | " |
| " | " | 1: 100 " | dark cherry-red and opaque | " |
| Cassia | brownish-yellow | 1:1000 " | brownish-red to hyacinth-red | black. |
| " | " | 1: 100 " | dark brown-red | " |
| Sassafras | yellowish | 1:1000 " | yellowish-brown | " |
| Star anise | pale yellow | 1:1000 " | dark wine-yellow | " |
| Valerian | pale greenish | 1: 100 " | brownish-yellow | " |
| Rue | slightly yellowish | 1: 100 " | brown-yellow | ash-gray. |
| Bergamotte | yellowish | 1:1000 " | dark yellow | " |
| " | " | 1: 100 " | brownish-red | " |
If these oxygenated oils are mixed with