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Now the effect of this will be that the dyestuff, partly in the fibre as a proper dye, and not a little on the fibre as if "smudged" on or painted on, will, on exposure to the weather, moisture, air, and so on, gradually oxidise, the great preponderance of iron on the fibre changing to a kind of iron-rust, corroding the fibres in the process, and thus at once accounting for the change to the ugly brownish shade, and to the rubbing off and rapid wearing away of the already too thin superficial coating of dyed felt fibre.
The recent closer combination of dyestuff industries of Germany, with the express purpose of meeting and destroying American competition after the war, is interesting as showing German methods. For a number of years the dye-stuff industry of Germany was practically controlled by six great companies, some of these companies employing as high as five hundred chemists in research work.
We must seek for an acid or acid body to use as mordant for our basic colour, and an acid or acid body that will form an insoluble precipitate or colour-lake with the dyestuff. An acid much used, and very valuable for this purpose, is tannic acid.
'A little dyestuff and three yards of cloth to help out a jest. Is it much to ask? 'Who is she? Thou art full young, as Sahibs go, for this devilry. 'Oh, she? She is the daughter of a certain schoolmaster of a regiment in the cantonments. He has beaten me twice because I went over their wall in these clothes. Now I would go as a gardener's boy. Old men are very jealous. 'That is true.
Another extremely sensitive indicator is the coal-tar dyestuff known as "Congo red"; the colour changes produced by it are exactly the inverse of those produced in the case of litmus, that is, it gives a blue colour with acids and a red colour with alkalis.
The consequence is a too slight penetration of the dyestuff into the inner pores of the fibres; indeed, in the logwood black dyeing of such proofed felt a great deal of the colour becomes precipitated on the outside of the fibres a kind of process of "smudging-on" of a black pigment taking place.
To neutralise this purple effect, a small quantity of a yellow dyestuff and a trifle of indigotin are added. A deep black is thus produced, faster to light than logwood black it is stated, and one that goes on the fibre with the greatest ease.
Evidently the way in which, the turmeric dyes the cotton is different from that in which the madder dyes it. The first is a yellow dyestuff, but it would be hard to assign any one shade or tint to Alizarin as a dyestuff.
It contained some four hundred and fifty tents, set on clipped grass along rolled and gravelled streets as straight as bricklayers' guide-boards; all about a paved square of ample size, on the rear of which was set up a gorgeous commander's tent of the whitest canvas, striped with red almost as deep, rich and glowing as the Imperial crimson, and manifestly meant to imitate it as closely as such a dyestuff could.
Quoting from an official American report, "Griesheim Elektron, prior to the war, had enormous works chiefly devoted to the manufacture of electrolytic chemicals and became an important factor in the dyestuff business only within recent years, when by absorption of the Oehler Works and the Chemikalien Werke Griesheim, its colour production reached a scale approaching that of the larger houses."
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