In order to determine the camphor content of essential oils (which contain no other carbonyl compounds) the gravimetric determination proposed by Aschan120 may be employed.
Procedure: Introduce about 1 g. of the oil, accurately weighed, into a test tube and dissolve the oil in 2 g. of glacial acetic acid. Add 1 g. of semicarbazide hydrochloride and 1.5 g. of freshly fused anhydrous potassium acetate. Triturate thoroughly with a glass rod, stopper the tube with a plug of absorbent cotton and heat three hours in a water bath at 70. Cool the mixture, add 10 to 15 cc. of water, stir thoroughly and transfer the precipitate quantitatively to a tared 4 to 5 cm. filter. Wash with water until all water soluble matter is removed, air dry, wash with petroleum ether and dry in air to constant weight. Determine the weight of semicarbazone from the increase in the weight of the filter. Calculate the content of camphor in the original oil by means of the following formula:
Percentage of camphor = 72.7p/s
where : p weight of semicarbazone in grams ;
            s = weight of oil in grams.
119 Drug & Cosmetic Ind. 46 (1940), 414.
120 Finska Apoth. Tidskrift (1925), 49. Chem. Abstracts 20 (1926), 1775.

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