INDIGO.

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Brazil Indigo occurs in small redtangular blocks, or irregular lumps : it isfirm, breaks readily, the fracfture is not conchoidal; it assumes, also, whenrubbed with the nail, a coppery hue, and is externally greenish-grey.

Carolina Indigo is in the shape of small lozenges, externally grey : both thelast-named sorts are superior in quality to the other American produdts.

Among the improvements Egypt owes to its last three rulers, the cultivationof indigo-producing plants is not one of the smallest: the result is, that forabout the last twenty-five years there has been in the market an excellentquality of this ware, met with in the shape of flattened cakes, of fine-grainedtexture, very light, and coloured either pure blue or pure violet-blue: it ispacked in boxes.

Senegal and Mauritius Indigos are rarely seen in the market, but are, gene-rally speaking, of very good quality.

Low qualities of indigo are charadterised by a dirty, more or less greenish,colour, a coarse and unequal texture, and great specific gravity; they do notadhere to the tongue, and do not become coppery by fridtion with the nail.Such are never of any real use to the dyer, notwithstanding the low price atwhich they are offered. The fadt that some samples of indigo contain onlyfrom 12 to 14 per cent of indigotin is of itself sufficient proof of the necessityof adopting scientific investigation for the proper valuation of this ware.Such indications are of immensely more value than the empirically obtained,often useless, valuation and sorting of the brokers. All indigos which containa large percentage of impurities are a loss to the dyer, since these cause bytheir presence a loss of colouring matter, which is rendered unavailable andinadtive.

The best kinds of indigo for use in the so-called cold-vat, for dyeing linenand cotton,* are the medium good qualities of Bengal and Guatemala, andespecially the reddish varieties : the inferior qualities just mentioned are lessinjurious when applied in the so-called hot-vats, used for dyeing wool; andthis branch of industry consumes the inferior kinds to a large extent. Forthe purpose of calico-printing the better qualities only of indigo are used.

The following are a few of the trade terms applied to indigo generally,without reference to the country of its produdtion : —

Sandy Indigo, containing much earthy matter.

Ribboned Indigo, exhibiting various shades of colour, running in the shapeof ribbons.

Spotted Indigo, the colour varying from spot to spot.

Burnt Indigo, when it happens that the ware, on pressure in the hand,falls to black pieces.

Large Squared Indigo, when the cakes are broken up into several largelumps.

Half Broken Indigo, when the cakes are broken in two only.

Coarse Granulated Indigo, the ware broken into comparatively smalllumps.

Cold Indigo, when the ware does not adhere to the tongue.

Big Indigo, s. very low quality, used possibly by the makers of laundry blues.

Since indigo is an expensive dye-material, and since its value depends notonly on the percentage of indigotin it contains, but also on its physical

* Cotton yarn, we need hardly state, is dyed blue in the hot copperas bath.