Botanic characteristics—
Curaçao Aloe—
Brownish black, opaque masses. Its fractured surface is uneven, waxy, and somewhat resinous.
Cape Aloe—
Dusky to dark brown irregular masses, the surfaces of which are often covered with a yellowish powder. Its fracture is smooth and glassy.
Powdered Aloe—
Yellow, yellowish brown to olive-brown in color. When mounted in a bland expressed oil, it appears as greenish yellow to reddish brown angular or irregular fragments, the hues of which depend to some extent upon the thickness of the fragments.
Identification—
A:
Powdered Aloe dissolves in nitric acid with effervescence, forming a reddish brown to brown or green solution.
B:
Intimately mix in a flask or bottle 1 g of finely powdered Aloe with 25 mL of cold water, shake the mixture occasionally during 2 hours, transfer to a filter, and wash the filter and residue with sufficient cold water to make the filtrate measure 100 mL: the color of the filtrate, viewed in the bulb of a 100-mL volumetric flask, is dark orange with Curaçao Aloe, and greenish yellow with Cape Aloe. The filtrate darkens on standing.
C:
To 5 mL of the filtrate obtained in
Identification test
B add 2 mL of nitric acid: the mixture exhibits a reddish orange color with Curaçao Aloe, and a reddish brown color which changes rapidly to green with Cape Aloe.
D:
Mix 10 mL of the filtrate obtained in
Identification test
B with 2 mL of ammonium hydroxide: the mixture exhibits an amber color with Cape Aloe, and a dark amber color with Curaçao Aloe.
Water, Method III 
921
:
not more than 12.0%, determined by drying at 105
for 5 hours. For Aloe that is not powdered, crush it in a mortar until it passes through a No. 40 sieve, and mix the ground material before weighing the sample.
Alcohol-insoluble substances—
Add about 1 g of powdered Aloe, accurately weighed, to 50 mL of alcohol in a flask. Heat the mixture to boiling, and maintain at incipient boiling for 15 minutes, replacing any loss by evaporation. Remove from the heat, and shake the mixture at intervals during 1 hour, pass through a small dried and tared filter paper or a dried and tared filtering crucible, and wash the residue on the filter with alcohol until the last washing is colorless. Dry the residue at 105
to constant weight: the weight of the residue does not exceed 10.0% of the weight of Aloe taken.
Assay—
Macerate about 2 g of Aloe, accurately weighed, in about 70 mL of water in a suitable flask. Shake the mixture during 8 hours at 30-minute intervals, and allow it to stand for 16 hours without shaking. Filter, and wash the flask and residue with small portions of water, passing the washings through the filter, until the filtrate measures 100.0 mL. Evaporate a 50-mL aliquot of the filtrate in a tared dish on a steam bath to dryness, and dry at 110
to constant weight. The weight of water-soluble extractive so obtained is not less than 50.0% of the weight of Aloe taken.
