What are essential oils?
Volatile oils are the odorous principles found in various plant parts. When they are exposed to air at ordinary temperatures they evaporate, therefore they are called volatile oils, ethereal oils, or essential oils. The last term is applied because the oils represent the "essences" or odor constituents of the plants. As a result, they are usually colorless, particularly when fresh, but with age they may oxidize and resinify, thus becoming darker. Therefore, storage should be in a cool, dry place, tightly stoppered, preferably full in amber glass containers.

Essential oils are highly concentrated plant extract (steam distilled, molecular or chemically extracted) - highly volatile (evaporate readily) with characteristic odors - many are non-oily (more like water than oil); though most are oily-feeling - usually lighter than water (most float on top of water) - insoluble in water (however, will impart odor to water) - soluble in alcohol, ether, fixed oils (vegetal), organic solvents - they dissolve grease, iodine, sulfur and phosphorous; reduce certain salts - generated or secreted by specialized plant cells

Physical Characteristics: although differing in their chemical constitution, they have many physical properties in common: boiling points vary from 160° to 240° C, densities are from 0.759 to 1.096, high refractive indices, most are optically active, specific rotation is often a valuable diagnostic property mixtures of many constituents.

The preceding is taken from The Aromatherapy Practitioner Correspondence Course.

Neroli, Orange blossom (a.k.a. neroli bigarade) / bitter orange tree flowers

Botanical name: Citrus aurantium var. amara
Family: Rutaceae
Country of Origin: Italy, Morocco, Tunisia, Guinea
Products: Essential oil (steam distilled); concrete, absolute

Note: 1) same tree also produces orange essential oil (fruit) & petitgrain (leaves)

Physical/chemical characteristics:

essential oil: oil Is obtained by steam distillation of the flowers and yields ca. 0.1%.; pale-yellow to amber, mobile oil which becomes darker and more viscous on aging.
concrete: extracted from freshly picked flowers with a solvent (usually petroleum ether); yellow-red liquid with typical flower odor

Organoleptic characteristics: powerful, light, refreshing floral, peculiar sweet-terpene topnote, poor tenacity.

Chemistry:

essential oil:
monoterpenes (35%): a-pinene, b-pinene, d-limonene, camphene, alcohols: phenylethyl, benzyl
terpene alcohols (40%): (-)-linalool, (+)-a-terpineol, geraniol, nerol
esters (>21%): linalyl acetate, neryl acetate, geranyl acetate
sesquiterpene alcohols (6%): trans-nerolidol, farnesols
aldehydes: 2,5-dimethyl-2-vinyl-hex-4-enal, decanal, benzaldehyde
ketones: jasmone(tr.)
nitrogen compounds (>1.5%): methyl anthranilate, indole
acids: (tr.): benzoic, palmitic, phenylacetic

floral water:
Rich in phenylethyl alcohol, methyl anthranilate, with phenylacetic acid, traces of jasmone

Traditional, Anecdotal and Esoteric uses:
Neroli is totally a fragrance trade product; it has no traditional aromatherapy uses; orange fruit used in traditional medicine, however doubtful the essential oil does same; internal use may cause some of following effects or they have been shown in vitro* studies) antidepressant, antiseptic, anti-infectious, antibacterial* (E.coli), antimycobacterial* (BK), antiparasitic* (ankylostoma, lamblia), anti-hypertension , antispasmodic, aphrodisiac, bactericidal, cicatrizant, cordial, cytophylactic, deodorant, emollient, fungicidal, hypnotic, sedative, digestive-carminative, calms CNS

Character: Yin (with high Yang)
Body type: Ectomorph
Number: 1
Crystals: Selenite (best), Herkemer Diamond, Fluorite, Rutilated quartz, Diamond, & Chrysoprase, Chalcedony
Chakra: 4, 8 & higher
Element: Fire, Air & Ether
Perfume Note: Mid to base
Astrological: Sun

Physiological uses:

Skin: thread veins, scars, stretch marks; dry, devitalized, oily, acne, mature and sensitive skin; improves elasticity

Respiratory System: bronchitis, pleurisy, pulmonary problems

Muscular System: useful for increasing muscle tone

Cardio-vascular: circulatory & arterial tonic, balances blood pressure, poor circulation; eases palpitations, varicosities, hemorrhoids

Gastro Intestinal System: chronic diarrhea, colic, colitis gas, spasm (nervous); calming effect on intestines, tonic effect on liver & pancreas; infant colic use floral water compress

Reproductive System: aphrodisiac; relieves emotional depression with PMS and menopause; aids labor (sustains uterine tone)

Mental Emotional: shock, stress, anxiety (test), depression, & insomnia due to depression, disappointment & sadness, mild hypnotic, tranquilizes sympathetic nervous system-can be very relaxing; instills peace, purity, aids in all spiritual work, reconnecting with higher self, promotes self confidence, ability to take initiative

Safety Data: tested (RIFM) at low dose (<2%) non-toxic, non-irritating, non sensitizing, non-photo-toxic; rare reports of dermatitis and photosensitivity; absolute tested non-sensitizing, non-irritating (m. watt, plant aromatics).