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The d modification is of the commonest occurrence, the other forms being only known as synthetic products; for this reason it is usually termed glucose, simply; alternative names are dextrose, grape sugar and diabetic sugar, in allusion to its right-handed optical rotation, its occurrence in large quantity in grapes, and in the urine of diabetic patients respectively.

American.—Specific gravity at 15° C., 0.906-0.920; optical rotation, -20° to -33°; total menthol, 50-60 per cent.; free menthol, 40-50 per cent.

The following figures may be taken as limits for pure oils:— French and Dalmatian.—Specific gravity at 15° C., 0.900-0.916; optical rotation, usually dextro-rotatory, up to +15°, but may occasionally be lævo-rotatory, especially if stalks have been distilled with the leaves; ester, calculated as bornyl acetate, 1-6 per cent.; total borneol, 12-18 per cent.; usually soluble in 1-2 volumes of 82.5 per cent. alcohol.

Specific gravity at 15° C., 1.180-1.187; optical rotation, Gaultheria oil, up to -1°, Betula oil, inactive; ester as methyl salicylate, at least 98 per cent.; refractive index at 20° C., 1.5354-1.5364; soluble in 2-6 volumes of 70 per cent. alcohol.

The article has the specific gravity at 15° C., 0.870-0.876; optical rotation, -12° to -14°; refractive index at 20° C., 1.463-1.464; and when estimated by acetylation, yields about 70 per cent. of alcohols.