The colourproducing reagent is added and the tints compared.
Coccinea, often confounded with the red oak, but with larger leaves, with long lobes ending in several acute points; they change to a brilliant scarlet with the first October frosts, giving one of the most striking of the various glowing tints that render the American forests so beautiful in autumn.
The bark, very dark externally, is an excellent tanning substance; the inner layers form the quercitron of commerce, used by dyers for communicating to fabrics various tints of yellow, and, with iron salts, yielding a series of brown and drab hues; the colouring property depends on a crystalline principle called quercitrin, of which it should contain about 8%.
Ihe great works of the Vatican are especially famous (more than 17,000 distinct tints are employed in their productions), and there are many other establishments in Rome.
This beautiful material presents a great diversity of tints, but a rich hyacinth red is common.