Salix Pharm. Edinb. Salix vulgaris alba arborefcens C. B. Salix Ger. Salix fragilis Linn. Common white willow: a pretty large tree, frequent in moist woods and hedges; producing loose spikes or catkins, either of imperfect barren flowers, or of seeds inclosed in down: it is the largest of the willows; and differs from the others, in the oblong pointed ferrated leaves being hoary on both sides, though most so on the lower, and in the branches not being tough.

(a) It is said that the marine add may be combined with vinous spirits as intimately as the others, and an ethereal fluid produced from the mixture, by applying the acid spirit to the vinous while both are resolved by fire into vapour; or more commodiously, by using the acid in a high degree of concentration, such as is obtained by distillation from a mixture of mercury sublimate with tin, commonly called the smoking spirit of Libavius, and proceeding with this spirit and spirit of wine, in the same manner as with the other acids. It is supposed that this acid, in distillation from metallic substartces, takes up a portion of the inflammable principle of the metal, which promotes its union with the vinous spirit.

The bark of this tree has lately been found an useful medicine in agues, of which many per-sons have been cured by taking a dram of the powdered bark every four hours during the inter millions, though in some cases it was neces-sary to join to it a little Peruvian bark (see the Philosophical Transactions for the year 1763). To the taste this bark discovers a pretty strong bit-terness and astringency: with solution of chalybeate vitriol, it strikes an inky blackness. These observations serve therefore to confirm what has been remarked under the head of the Peruvian bark, that in the distempers where that valuable medicine takes place, other bitters and astrin-gents are likewise useful, though in an inferiour degree. The astringency of the willow bark is extracted both by water and spirit; and the black matter, produced by adding vitriol to the watery infusion, is not disposed to precipitate.