=Properties and Uses.=—These Vat dyes are not all of equal value, but as a class they are, distinctly, the fastest of any as yet introduced; and the best of them may properly be considered as the most permanent coloring agents of any sort or kind that have ever yet appeared on the earth. They not only far surpass in this respect the best of the vegetable dyestuffs, with the possible exception of the very best qualities of Turkey red, but in resistance to chemicals and outside agencies of various sorts, are much better than the best mineral colors. This is so much the case that the modern specifications for dyed cloth for Government purposes, as for instance the khaki uniforms for soldiers in active service, which up to a year or two ago were dyed with iron buff modified with oxide of chromium, have been raised, in one country after another, until they exclude every class of dyestuffs except these new Vat colors. During the last year or two these dyes have been introduced, though with some difficulty, into commerce, and it is possible to obtain shirtings and other printed goods, dyed in permanent colors, so permanent indeed that the cloth will wear completely out before the color changes in the slightest. The extra cost of the dyestuffs, and the comparative difficulty of dyeing to shade, furnish an excuse for increasing the price of the goods. And the perhaps not unnatural disinclination of the shopkeepers to push the sale of materials which, in their opinion, are quite unnecessarily fast, has combined with the cost to delay the general adoption of these remarkably valuable coloring agents. For craftsmen, however, where the price of the dyestuffs constitutes such a small percentage of the cost of the finished article, and where the absolute permanence of the color is of the utmost importance, these colors are most useful. They are not to be used, excepting under special circumstances, for animal fibres—wool, silk, leather, feathers, etc.—for fear of injuring the materials by the action of the caustic alkali. But on cotton and linen, both in direct or resist dyeing, and for stencil work, there are no colors to compare with them in fastness, not excepting even the very best of the Sulphur colors. DYEING DIRECTIONS These dyes are all applied, just like indigo, in an alkaline hydrosulphite vat. The colors are applied in paste form, usually 20% strong, or at any rate equivalent in strength to a 20% paste of pure indigo. Care must be taken to thoroughly mix and stir up this paste with a glass rod, in the original package, each time it is used, so as to keep its composition uniform.