292 SYLVA AMEBIC ANA. 



hand, if the evaporation be conducted too slowly, the coloring 

 matter suffers another change, and soon spoils by keeping. The 

 decoction of quercitron is of a yellowish-brown color, which is 

 darkened by alkalies, and brightened by acids. A solution of 

 alum being added to it, separates a small proportion of the 

 coloring matter, which subsides in the form of a deep yellow 

 precipitate. The solutions of tin produce a more copious 

 precipitate, and of a beautiful, lively, yellow color. Sulphate of 

 iron causes a copious olive precipitate ; sulphate of copper, a 

 yellow of an olive cast. To dye wool, it is sufficient to boil the 

 quercitron with an equal weight of alum : in dipping the stuff 

 the deepest shade is given first, and afterwards the straw color : 

 enliven the tint the stuff may be passed, in coming out of the 

 dye through water whitened with a small portion of chalk : but 

 a brighter color is obtained by means of a solution of tin. 

 Quercitron may be substituted for woad, in imparting all the 

 shades of yellow to silk. It is highly valuable as an article of 

 commerce, which has often been sold at '40 or $50 a ton. 

 Large quantities are annually exported into Europe from the 

 ports of the Middle States. 





