The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918
Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.
Quercitron Bark
Commercial Preparations.
Flavin.
This is the most important commercial preparation of quercitron bark; it seems to have been first imported into this country from America. The details of its manufacture have been guarded with much secrecy, and analyses of commercial samples show that different methods have been adopted by different makers. Some specimens consist essentially of quercitrin, and are known as yellow flavin, whilst others contain only quercetin, and are known as red flavin. The former have probably been prepared by merely extracting the bark with water and high-pressure steam, or, as it is said, with steam only at a temperature of 102-103°.
The best qualities of flavin are those in which the colouring matter is present as more or less pure quercitrin, and entirely free from woody fibre. Red flavin is prepared by rapidly extracting the powdery portion of rasped quercitron bark with ammonia or other alkali, and boiling the solution with sulphuric acid. The precipitate thus produced is ultimately collected, washed with cold water till free from acid, and finally dried. Flavin of this character has about sixteen times the tinctorial value of quercitron bark. It is not very soluble, but it yields with aluminium, and especially with tin mordants, much more brilliant colours than quercitron bark itself.
Patent bark.
Patent bark, or "commercial quercetin," is a preparation of quercitron bark analogous to the garancin made from madder. It is manufactured in a similar manner, viz. by boiling, for about two hours, 100 parts finely ground quercitron bark, 300 parts water, and 15 parts concentrated sulphuric acid. The product is collected on a filter, washed free from acid, and dried. The yield is about 85 per cent, of the bark employed, while its colouring power is much greater. It seems to have been first manufactured in 1855 by Leeshing.
Bark-liquor.
Bark-liquor is simply an aqueous extract of quercitron bark, and is sold with a specific gravity of 1.66-1.255.
Application.
Quercitron bark, patent bark, and bark extracts have been largely employed by the calico and woollen printer. The latter are used in the preparation of steam-yellows, olives, chocolates, etc., in conjunction with aluminium, tin, chromium, and iron mordants. The former at one time found employment in conjunction with garancin for the production of various compound shades, e.g. chocolate, dull red, orange, etc. Now they may be used in a similar manner along with alizarin. When used alone, quercitron bark and patent bark give, with aluminium mordant yellow, with tin orange, with chromium olive-yellow, with iron greenish-olive colours.
Flavin is chiefly serviceable in wool dyeing for the production, in single-bath, of bright yellow and orange, fast to milling, and was at one time largely used along with cochineal to obtain a bright scarlet. The mordant employed is stannous chloride and oxalic acid or cream of tartar.
On cotton all the quercitron colours are but moderately fast to light; on wool and silk the chromium, copper, and iron colours are fairly fast, whereas the aluminium and tin colours are only moderately so.
