Good liquid storax should yield to 90 per cent. alcohol at least so much soluble matter that the dried residue of the filtered alcoholic solution amounts to 65 per cent. of the quantity of storax.
Ordinary liquid storax, which has not been stored too long, contains 10 to 20 per cent. of water and about the same quantity of impurities (fragments of plant tissue) which remain behind on treatment with the above-mentioned solvents.
Liquid storax is said to be adulterated with the turpentines of some species of larch and pine. Such adulteration is primarily detected, according to Hager, by the specific gravity. Take up a drop of the balsam with a knitting-needle, and by heating the needle make it fall into a cold solution of 1 part common salt and 8 parts water. On stirring, the drop must sink, otherwise adulteration with turpentine is very likely. Next bring 5 grammes of the storax into a test-tube, melt it in the water-bath, add ½ volume of absolute alcohol, and mix by shaking; then compound the mixture with several times its volume of petroleum-ether, shake vigorously, allow to settle, and decant the layer of petroleum-ether. Repeat twice this shaking with petroleum-ether; then evaporate the petroleum-ether solution in a tared flask in the water-bath. The residue remaining after evaporation is colorless, bluish opalescent, and of an agreeable odor; in the presence of turpentine it is yellowish and has the, not to be mistaken, odor of turpentine.
_Storax in grains_ consists of round, longish grains of a brown-black color and smooth, lustrous surface, which soften by the warmth of the hand. It is nothing but liquid storax brought into a granular form and by storing freed more or less from impurities.
_Ordinary storax_ (_Styrax calamitus_ or _St. vulgaris_) is an artificial product prepared by mixing liquid storax with various comminuted vegetable substances. Formerly the above-mentioned bark of the storax tree (_Cortex thymiamatis_) was only used for this purpose, but at present sawdust and exhausted cinnamon are also taken. This storax forms a reddish or brown-black, humus-like mass, which is generally moist. When dried it is very friable and has a storax-like odor distinctly calling to mind that of cinnamon. Good qualities are abundantly covered with crystalline efflorescences (of cinnamic acid and styracin); poorer qualities prepared with the addition of sawdust have a musty odor. The admixed vegetable tissue can, according to Wiesner, be readily recognized by boiling the storax with alcohol, and after washing treating with dilute chromic acid, to which a small quantity of sulphuric acid has been added.