Chemical Composition—Logwood was submitted to analysis by Chevreul as early as the year 1810,[828] since which period all contributions to a knowledge of the drug refer exclusively to its colouring principle Hæmatoxylin, which Chevreul obtained in a crystallized state and called Hématine. The very interesting properties of this substance have been chiefly examined by Erdmann (1842) and by O. Hesse (1858-59).

Erdmann obtained from logwood 9 to 12 per cent. of crystallized hæmatoxylin, which he showed to have the formula C₁₆H₁₄O₆. In a pure state it is colourless, crystallizing with 1 or with 3 equivalents of water, and is readily soluble in hot water or in alcohol, but sparingly in cold water or in ether. It has a persistent sweet taste like liquorice. The crystals of hæmatoxylin acquire a red colour by the action of sunlight, as likewise their aqueous solution. They are decomposed by ozone but not by pure and dry oxygen. In presence of alkalis, hæmatoxylin exposed to the air quickly yields dark purplish violet solutions, which soon acquire a yellowish or dingy brownish colour; hence in analytical chemistry hæmatoxylin is used as a test for alkalis.

By the combined action of ammonia and oxygen, dark violet crystalline scales of Hæmateïn, C₁₆H₁₄O₆ + 3 OH₂, are produced.[829] They show a fine green hue, which is also very commonly observable on the surface of the logwood chips of commerce. Hæmateïn may again be transformed into hæmatoxylin by means of hydrogen or of sulphurous acid.

Hæmatoxylin separates protoxide of copper from an alkaline solution of the tartrate, and deviates the ray of polarized light to the right hand. It is not decomposed by concentrated hydrochloric acid; by melting hæmatoxylin with potash, pyrogallol (pyrogallic acid, C₆H₆O₃) is obtained. Alum and the salts of lead throw down precipitates from solutions of hæmatoxylin, the latter being of a bluish-black colour. Logwood affords upon incineration 3·3 per cent. of ash.

The colouring matter being abundantly soluble in boiling water, an Extract of Logwood is also prepared on a large scale. It occurs in commerce in the form of a blackish brittle mass, taking the form of the wooden chest into which it is put while soft. The extract shares the chemical properties of hæmatoxylin and hæmateïn: whether it also contains gum requires investigation.

Production and Commerce—The felling and shipping of logwood in Central America have been described by Morelet,[830] who states that in the woods of Tabasco and Yucatan the trade is carried on in the most irrational and reckless manner. By advancing money to the natives, or by furnishing them with spirits, arms, or tools, the proprietors of the woods engage them to fell a number of trees in proportion to their debts. This is done in the dry season, the rainy period being taken for the shipment of the logs, which are conveyed chiefly to the island of Carmen in the Laguna de Terminos in South-western Yucatan, and to Frontera on the mouths of the Tabasco river, at which places European ships receive cargoes of the wood.

In 1877 the export of Laguna de Terminos amounted to 528,605 quintals (one quintal = 46 kilogrammes), that from Port-au-Prince, Hayti, in 1872, nearly to 90,000 tons.

Four sorts of logwood are found in the London market, namely Campeachy, quoted[831] at £8 10s. to £9 10s. per ton; Honduras, £6 10s. to £6 15s.; St. Domingo, £5 15s. to £6; Jamaica, £5 2s. 6d. to £5 10s. The imports into the United Kingdom were valued in 1872 at £233,035. The quantities imported during that and the previous three years were as follows:—

1869187018711872
50,458 tons. 62,187 tons. 39,346 tons. 46,039 tons.

In 1876 the import was 64,215 tons, valued at £415,857. The largest quantity is supplied by the British West India Islands. Hamburg also imports annually about 20,000 tons of logwood.