This section is from the book "A Text Book Of Materia Medica, Being An Account Of The More Important Crude Drugs Of Vegetable And Animal Origin", by Henry G. Greenish. Also available from Amazon: A Text Book of Materia Medica : Being an Account of the More Important Crude Drugs of Vegetable and Animal Origin.
Socotrine Aloes. This variety is stated in the British Pharmacopoeia to be derived from Aloe Perryi, Baker, and probably other species. It is brought by Arab traders from the east coast of Africa, the island of Socotra (600 miles west of Aden), and possibly also from the coast of Arabia, to Bombay, whence it is exported to Europe. It arrives usually in kegs or tins, or occasionally in large barrels, and commonly has a pasty, semi-liquid, or even treacly consistence. It is then of a brownish yellow colour and quite opaque, but if not too viscid it separates on standing into a clear, dark brown, supernatant liquid and a dark yellow sediment which, under the microscope, is seen to consist of minute, prismatic crystals (aloin). The odour of the fresh aloes is usually remarkably unpleasant, but this may change when the aloes is kept under certain (not at present precisely known) conditions to a rather agreeable fragrance that has been compared to myrrh and saffron.
As this variety of aloes contains a varying amount of water, and is not, as imported, in a suitable condition for use in pharmacy, it must be dried at a gentle heat, best by exposing it on wooden trays in a warm room. It then forms hard, dark brown or sometimes, if dried at too high a temperature, nearly black masses, breaking with a dull, waxy, uneven, often porous fracture, and possessing a strong, characteristic unpleasant odour and an extremely bitter, nauseous taste. It should be almost entirely soluble in alcohol, and yield about half its weight to cold water. Small splinters are opaque, but mounted in a drop of almond oil and examined under the microscope they exhibit numerous minute prismatic crystals (of aloin) embedded in a transparent, dark yellowish brown mass. This aloes therefore belongs to the class of aloes known as livery or hepatic aloes. From other aloes it may be distinguished by moistening a little of the powder with nitric acid, when a reddish or yellowish brown colour is produced.
2. Zanzibar Aloes, which is sometimes regarded as a variety of Socotrine, is commonly poured into skins which are then packed in cases (' monkey-skin ' aloes). It is usually hard, but is sometimes soft, and then the contents of the case become compacted into a solid mass. It has a liver-brown colour, and a dull waxy, but nearly smooth and even fracture. In this respect it differs from the foregoing, which breaks with an uneven fracture, as it does also in its odour, which is characteristic and strong but not disagreeable.
Both the foregoing varieties of aloes are usually hepatic, a fact that points to a slow concentration of the aloe juice, possibly by spontaneous evaporation. Both occur also in the vitreous variety, but East African aloes is seldom imported in this condition.