It is reported that the oil distilled in India is occasionally adulterated with castor oil or with the fatty oil from the seeds of the sandalwood tree which is used as a lamp oil. Admixtures of sesame oil, liquid paraffin and linseed oils are said not to be uncommon in India.
The best method to determine the purity of sandalwood oil or to ascertain the amount of adulterant present, is to determine its santalol percentage. Good oils contain mostly from 94 to 98 p. c, but never below 90 p. c. of santalol.
Parryl) was the first to suggest the test for santalol Dy heating the oil with glacial acetic acid in a closed container to 150°, thus converting the alcohol into its acetate and to saponify the ester by means of alcoholic potassium hydroxide. According to Schimmel & Co.2), however, it is more expedient to determine alcohols in volatile oils by means of acetic acid anhydride.
The process is carried out in the following manner:8)
In an acetylation flask 10 cc. of sandalwood oil are mixed with an equal volume of acetic acid anhydride, 2 g. of fused sodium acetate and a few fragments of porous tile are added and the mixture is heated to gentle boiling for an hour. Upon cooling some water is added to the contents of the flask, the mixture heated for 1/4 hour on a water bath with occasional shaking in order to decompose the excess of acetic acid anhydride. The mixture is again allowed to cool, the oily layer separated from the aqueous layer by means of a separating funnel, and the oil washed with water or, better still, with sodium chloride solution until the wash water remains neutral. Of the acetylized oil, dried with anhydrous sodium sulphate, 1,5 to 2 g. are saponified with 20 cc. of half normal alcoholic potassium hydroxide solution after any free acid that may have remained in the oil has been carefully neutralized. The amount of potassium hydroxide consumed is ascertained by titration with half-normal sulphuric acid.
1) Pharmaceutical Journ. 55 (1895), 118.
2) Report of Schimmel & Co. October 1895, 43.
3) See also vol. I, p. 570.
The santalol content C15H24O1) is then ascertained by means of the following formula 2): P = a. 11 / s - a.0,021 a = the number of cc. of half-normal potassium hydroxide solution.
P=the santalol content of the original oil.
s = the amount in grams of acetylated oil used for saponification.
Frequently the determination of the physical constants suffices to distinguish a pure oil from an adulterated one. In all cases, however, adulterations can be definitely ascertained by means of the santalol test which has been introduced by the more recent pharmacopoeias. Hence it is unnecessary to resort to the wholly unscientific and misleading color reactions that are still recommended occasionally3).