Definition. - The purified fat of the wool of sheep, freed from water. The hydrous wool-fat, which contains "not more than 30 per cent. of water," is still retained in the Pharmacopoeia; if this be heated on the water-bath, with stirring, until it ceases to lose weight, it is converted into adeps lanae.

In making certain ointments, the water contained in hydrous wool-fat is objectionable; for such preparations adeps lanae is preferable.