As the British extended their trade through the Red Sea and Indian Ocean in the late 18th and early 19th centuries, there were a number of books written about the trade items and how to procure them at various ports. One of the most important was William Milburn’s Oriental Commerce, first published in 1813 and revised in an 1825 edition [https://catalog.hathitrust.org/Record/001123449] after the death of the author. The full text of the 1825 edition is available at archive.org. There is a lengthy discussion on trade through the port of Mocha, although very little on Aden, which was not very important at the time until the British took it over after 1839. I attach below the section on trade items available at Mocha (Milburn 1825:71-77).
ARTICLES TO BE PROCURED AT MOCHA, WITH DIRECTIONS
ACACIA, the inspissated juice of a thorny plant, growing in Arabia, and other parts:—two sorts are known, Vera and Germanica. The former is a gummy substance, usually firm, but not very dry. It is met with in round masses, enclosed in thin bladders, from four to eight ounces weight; outwardly a deep brown, inclining to black; of a lighter brown within, inclining to red or yellow. The Germanica is a juice expressed from the unripe fruit of the sloe bush, and differs from the preceding, in being harder, heavier, darker, sharper in taste, yielding its astringency to rectified spirit; whereas the other is not at all dissoluble by spirit. The Vera should have little or no smell; applied to the tongue, it should soften quickly, imparting a rough, not very ungrateful taste, followed by a sweetness. If quite pure, it dissolves totally in water; if otherwise, the impurities remain.
ACORUS, or CALAMUS AROMATICUS, (Bach, Hind. Vacha, S an.) is a reed, or knotty root, about the size of a little finger, several inches long, reddish externally, internally white, full of joints, somewhat flatted on the side, of a loose spongy texture ; smell strong, taste warm, bitterish, and aromatic. They should be chosen tough, cleared from fibres, and free from worms, to which it is very subject.
ASPHALTUM is a solid shining bitumen, of a dusky colour outside; within of a deep black, found in many parts of Egypt. A thin piece appears of a reddish colour, when placed between the eye and the light. It has no smell when cold, but acquires a slight one by friction ; when exposed to heat, it liquifies, swells up, and burns with a thick smoke, the smell of which is strong, acrid, and disagreeable. It is occasionally adulterated with pitch; but the fraud may be discovered by means of spirits of wine, which dissolve the pitch, and only take a pale colour with Asphaltum.
BALM OF GILEAD, or Balsam of Mecca, is a resinous juice that distils from an evergreen tree, or shrub, growing between Mecca and Medina; it is much used by the Asiatic ladies as a cosmetic. The tree is scarce; the best sort is said to exude naturally, but the inferior kinds are extracted from the branches by boiling. It is at first turbid and white, of a strong pungent smell, a bitter and acrid taste; upon being kept some time, it becomes thin, limpid, of a greenish hue, then of a golden yellow, and at length of the colour of honey. This article, being scarce and valuable, is very liable to adulteration. The following methods are recommended to discover imposition Cause a drop or two of the liquid balsam to fall into a glass of clear water; if the drop go to the bottom without rising again to the surface, or if it continue in a drop like oil, the balsam is adulterated. If, on the contrary, it spreads upon the surface of the water, like a very thin cobweb, scarcely visible to the eye, and being congealed, may be taken up with a pin or small straw, the balsam is pure and natural. Or if the pure balsam be dropped on woollen, it will wash out; but if adulterated, it will not. The genuine, dropped into milk, coagulates it. When a drop of the pure balsam is let fall on red hot iron, it gathers itself into a globule ; but oil or spurious balsam runs, and sheds itself all round. The genuine balsam also feels viscid and adhesive to the fingers. If sophisticated with wax, it is discovered by the turbid colour, never to be clarified; if with honey, the sweet taste betrays it; if with resins, by dropping it on live coals, it yields a blacker flame, and of a grosser substance than the genuine. When the balsam is too thick to be taken out of the bottle, it need only be placed near the fire, the smallest degree of heat liquifying it. The bottles must not be quite full, lest they should break, as the balsam is apt to rarify.