EXTRACTS OF DYE-WOODS.

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to extra# the colouring matters of dye-woods by means of weak solutionsof soda, potash, or ammonia, caustic or carbonated, and to neutralise thedecodtion thus obtained by the cautious addition of an acid. Others havereversed the method, treating the dye-ware first with an acid or an acid salt,and then neutralising with an alkali. Processes of this nature have beenpatented by Leeshing, No. 1160 (1855), an ^ by Roberts and Dale, No. 1988(1857). The objection to operations of this nature is, that even brief contadtwith alkaline liquids, especially at an elevated temperature, impairs the beautyof most of the colouring matters concerned. The utilisation of the exhaustedwood also is a matter of importance; an attempt has been made to manu-facture acetic acid from the residues, but this requires complicatedapparatus; perhaps the utilisation of this material along with other sub-stances, as compressed artificial fuel, might be worth while trying.

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