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.
Persian-berry lake is prepared by extracting Persian berries two or three times with boiling water, dissolving alum in the combined and filtered liquors, and then precipitating with sodium carbonate, taking care to avoid excess. The precipitate is collected on a filter, washed, and sold in the form of paste. This lake, containing much starch, and sold in the dry form, is said to be employed in the colouring of sweetmeats.
Persian-berry carmine is produced if stannous chloride is employed instead of alum in the above process. It is a bright orange-lake employed by calico-printers.
Persian-berry lakes may also be made after the manner of Vienna lake, i.e. with the use of chalk, alum, and starch.
It is essential to employ only freshly prepared decoctions if bright coloured lakes are desired.
Quercitron-yellow lake, Flavin-lake, or Dutch pink can be made according to the method adopted in the case of Venetian lake, by precipitating a decoction of quercitron bark containing alum with chalk. The methods employed in making yellow lakes from Persian berries may also be used. To ensure bright colours the decoction of quercitron bark is clarified by adding a little gelatin solution, thereby removing the tannic acid. Sometimes milk of lime is used instead, taking care to avoid excess.
It is said that these quercitron colours retained their intensity by gaslight better than all other vegetable yellows, and were thus of value for theatre decorations, etc.
The yellow natural colouring matters, especially flavine and Persian berries, are still in some demand for the production of green lakes by combination with basic green artificial colouring matters.
The yellow lake is first prepared and a solution of the coal-tar colour precipitated upon it by tannin and tartar emetic. A partial precipitation of the basic colour is effected by the tannic acid in the vegetable colour, but must be completed by a further addition. These lakes are used for wall-papers and for colouring toys.
Stil de Grain was a low quality of Dutch pink, and English and Italian pinks other qualities of quercitron bark yellow lakes.
Ei kommentteja :
Lähetä kommentti