A Dictionary of Arts: Weld.

A Dictionary of Arts, Manufactures, and Mines; containing A Clear Exposition of Their Principles and Practice

by Andrew Ure, M. D.;
F. R. S. M. G. S. Lond.: M. Acad. M. S. Philad.; S. PH. DOC. N. GERM. Ranow.; Mulh. Etc. Etc.

Illustrated with nearly fifteen hundred engravings on wood
Eleventh American, From The Last London Edition.
To which is appended, a Supplement of Recent Improvements to The Present Time.

New York: D Appleton & company, 200 Broadway. Philadelphia: George S. Appleton, 148 Chestnut St.
MDCCCXLVII

1847

WELD (Vouëde, Fr.; Wau, Gelbkraut, Germ.), is an annual herbaceous plant, which grows all over Europe, called by botanists Reseda luteola. The stems and the leaves dye yellow; and among the dyes of organic nature, they rank next to the Persian berry for the beauty and fastness of color. The whole plant is cropped when in seed, at which period its dyeing power is greatest; and after being simply dried, is brought into the market.

Chevreul has discovered a yellow colouring principle in weld, which he has called luteoline. It may be sublimed, and thus obtained in long needle-form, transparent, yellow crystals. Luteoline is but sparingly soluble in water; but it nevertheless dyes alumed silk and wool of a fine jonquil color. It is soluble in alcohol and ether; it combines with acids, and especially with bases.

When weld is to be employed in the dye-bath, t should be boiled for three quarters of an hour; after which the exhausted plant is taken out, because it occupies too much room. The decoction is rapidly decomposed in the air, and ought therefore to be made only when it is wanted. It produces, with
Solution of ising-glass - a slight turbidity.
Litmus paper - a faint reddening.
Potash ley - golden yellow tint.
Solution of alum - a faint yellow.
protoxide salts of tin - a rich yellow precipitation.
Acetate of lead - ditto
Salts of copper - a dirty yellow-brown precipitation.
Sulphate of red oxide of iron - a brown, passing into olive.

A lack is made from decoction of weld with alum, precipitated by carbonate of soda or potassa. See YELLOW DYE.