CHAPTER X.

REVIEW OF THE METHOD OF APPLYING ALBUMENOID SUBSTANCES IN THEFIXING OF COLOURS.

'T'HE use of albumenoid substances for the fixing of colours has become soextended, that, notwithstanding the high price, there is a constantlyincreasing demand for these materials. Their method of adtion is twofold.In some instances there is a genuine chemical combination between thecolouring-matter and the nitrogenous albumenoid compound. When, forinstance, aqueous solutions of aniline violet (indisine), and albumen areprinted upon cotton, the colour when dry appears very dull and without gloss;also, it is not fixed, but may be removed from the cloth by simply steeping incold water. After steaming, however, the albumen coagulates, and a truecombination is formed between the colouring-matter and the albumen on theone hand and the cotton on the other. In this instance the albumen a&sas a true mordant. But where albumen is employed to cause a very finely-divided insoluble powder, as ultramarine, to adhere to cloth, and is nextexposed to steam-heat, it serves merely as an adhesive, and its adtion ispurely mechanical. This application of albumen is due originally toM. Blondin de la Glacie’re, who, in the year 1820, made the first attempt tofix by means of albumen the brilliant blue colour derived from the lapis lazuli,or native ultramarine. As might have been expedted from the exceedinglyhigh price of native ultramarine, which is worth, weight for weight, morethan gold, the application remained inutilised for several years, owing aswell to the few varieties of pigments. Egg-albumen, as a fixing agent, wasintroduced into this country in 1847; and among- the many pigments appliedin this manner may be mentioned—Guignet’s green, several ochrous com-pounds of iron, Vermillion, zinc-white, some chrome colours, and vegetablelakes.

Albumen, in other words, white of egg, is best adapted to the pradticalfixation of colour, and would be unrivalled were it not for its high price, andfor the consideration that its employment withdraws from use as animal foodan enormous quantity of eggs. The best mode of effedting the solution of thedried commercial albumen is in tepid water, which should not be at a highertemperature than 113 0 to 122 0 F. (45 0 to 50° C.) ; the albumen should be addedgradually, and the solution constantly stirred, to prevent the particles ofalbumen agglutinising. The water should on no account be added to thedried and powdered albumen. The proportion of dry material to the litre ofliquid varies according'to the specific use for which it is intended, but 300 grms.to the litre is an average quantity. Since white of egg can never be obtained