black ash1
/ˌblak ˈaʃ/North American
noun
A North American ash, Fraxinus nigra (formerly called F. sambucifolia), found in wetlands in the north-eastern United States and eastern Canada; (also) the timber of this tree, which can be separated into flexible strips by pounding and is used in basket-making and cooperage.
Origin
Late 17th century. From black + ash. The reason for the name is uncertain: it may refer to the tree's dark brown heartwood, or it may refer to the appearance of the leaves, in contrast to those of the white ash.
black ash2
/ˌblak ˈaʃ/Chemistry. Now historical
noun
In the manufacture of sodium carbonate by the Leblanc process: a mixture of sodium carbonate and calcium sulphide formed at an intermediate stage, which is washed (lixiviated) with water to obtain the pure carbonate.
Origin
Early 19th century; earliest use found in The Repertory of Arts. From black + ash.