Oil of cinnamon or cassia depends entirely upon the amount of cinnamyl aldehyde it contains. Oil of the true cinnamon bark (cinnamomum Zeylonicum) is the finest essential oil to be had. It is worth $5 per pound, while common cassia is worth only about seventy cents. True cinnamon oil is obtained in Ceylon and is of a golden color when fresh, with an aromatic odor, and is very pungent, being powerful enough to blister the tongue, but varies by age from cherry to yellow-red, the paler varieties being the most esteemed. Cinnamon leaf is redistilled in London to obtain the desired color, although at a loss of about 10 per cent. (formula C_{ 10}H_{ 14}), with a small quantity of benzoic acid. Fine cinnamon oil has a taste of intense sweetness, far sweeter than sugar, and a clove-like taste is at first developed. It is largely used in perfumery and medicine. Ceylon ships about 15,000 to 40,000 ounces annually. China exports as much. After a time it loses its sweetness and is no better than cassia oil. The tree yields essential oils from the leaves, bark, and root, each oil differing in composition and value, which accounts for the many different grades or prices for cinnamon oil found on the market. Cinnamon and cassia oils are of the same chemical compositions, their value being estimated by the amount of cinnamyl aldehyde they contain. That obtained from the roots is light, while that obtained from the leaves is so heavy as to sink in water.
There is but a small amount of oil in the bark, the yield being but 1 to 1.5 per cent.; six and one-half ounces of heavy oil and two and one-half ounces of light oil to eighty pounds of bark. It consists chiefly of cinnamyl aldehyde or the hydride of cinnamyl and a variable quantity of hydrocarbon. The oil derived from the coarser bark is a dark-brownish color. The oil distilled from the true bark is worth about eighteen times as much as the oil distilled from the leaves or leaf stalk or flower stalk. The latter oil is chiefly of eugenol, a hydrocarbon having an odor of cymene, a little benzoic acid and cinnamyl aldehyde. When mixed with the young twigs and cassia buds of cassia shrubs, this oil becomes a beautiful bright oil of excellent taste—characteristics which denote a higher percentage of aldehyde. Twigs show a familiar sweet cinnamon taste, but they yield a smaller percentage of essential oil than is distilled from the leaves, and has a specific gravity of 1.45 at 15 degrees C., showing 90 per cent. of aldehyde. The leaves yield sweet oil at 15 degrees C., specific gravity 1.056, aldehyde 93. Cassia buds yield essential oil 1.550 per cent., specific gravity 1.026, aldehyde 80.4 per cent. Stalk of cassia leaves, leaf stalk, and young twigs mixed yield essential oil 0.77 per cent., gravity 1.055, aldehyde 93 per cent.