By distillation with quicklime, E. Robiquet (1846) obtained Aloïsol, a yellowish oil, which Rembold (1866) proved to be a mixture of dimethylated phenol (Xylenol)
| C₇H₃ |  | (CH₃)₂ |
| OH |
Nitric acid forms with Barbadoes aloes, but still better, as Tilden has shown, with barbaloïn, Aloëtic Acid, C₁₄H₄(NO₂)₄O₂, Chrysammic Acid, C₁₄H₄(NO₂)₄O₄, and finally Picric Acid, together with Oxalic Acid. The first two of these acids are distinguished by the splendid tints of their salts, which might be utilized in dyeing.
Chlorine, passed into an aqueous solution of aloes, forms a variety of substitution-products, and finally Chloranil, C₆Cl₄O₂.
When somewhat strongly heated, aloes swells up considerably, and after ignition leaves a light, slow-burning charcoal, almost free from inorganic constituents. Ordinary Cape aloes, for example, dried at 100° C., leaves only 1 per cent. of ash.
Commerce—There were imported into the United Kingdom in the year 1870, 6264 cwt. of aloes. Of this quantity, South Africa shipped 4811 cwt.; and Barbados 970 cwt. The remainder was probably furnished by Eastern Africa.
The commercial value of the varieties of aloes is very different. In 1874, Barbados Aloes was quoted in price-currents at £3 5s. to £9 10s. per cwt.; Socotrine at £5 to £13; while Cape Aloes was offered at £1 10s. to £2. In England, the first two alone are allowed for pharmaceutical preparations. Even the Veterinary Pharmacopœia[2581] names only Aloë Barbadensis. Cape Aloes is esteemed on the Continent, and chiefly consumed there.
Use—Aloes is a valuable purgative in very common use, it is generally given combined with other drugs.
Adulteration—The physical characters of aloes, such as colour of the powder, odour, consistence and freedom from obvious impurity, coupled with its solubility in weak alcohol, usually suffice for determining its goodness.