Another cold BLUE vat for linen and cotton.

The indigo is to be powdered, and put into warm water with sulphate of iron, in quantity twice the weight of the indigo, to which is also to be added, the same weight of fresh-burnt lime. The water should be only sufficient to mix it thick at first; keep it stirred; and, as it becomes dissolved and green under the surface, increase the water, often stirring and trying the mixture, by putting in a pattern between the stirrings, at some hours distance, between each pattern, and increasing the water: in twenty-four hours it will be fit for use.

Solution of indigo for penciling printed muslin, &c.

To twenty-five gallons of water, add sixteen pounds of indigo, and thirty pounds of carbonate of potash; when mixed, and placed over the fire, as soon as the mixture begins to boil, add quicklime, by a little at a time, to render the alkali caustic; then twelve pounds of red orpiment, and boil till it will give a yellow colour to transparent glass.

This form is from Haussman. Were the author to make this solution of indigo, he would first make the alkali caustic with lime, and then put the clear liquor to the other materials.

Mr. M'Kernan gives another form for pencil blue with indigo: the principal differences between which and the above, consist in adding equal parts of brown sugar and gum senegal to it, which, in regard to the addition of the gum, is, we presume, a great improvement.

Dr. Ure (Notes to Berthollet, vol. ii. page 437.) gives a similar form from Vitalis, for topical or pencil blue; but he adds, it was much used formerly. Another blue, of less permanence but more brilliance, is now preferred; it is made thus:—

Into an earthen pot four ounces of finely ground and sifted Prussian blue are to be put. Over this must be slowly poured, stirring all the while, sufficient muriatic acid to bring it to the consistence of syrup. The mixture is to be stirred every hour for a day, and afterwards thickened with from four to eight pots (of two litres each; a litre French contains about two wine pints;) of gum-water, according to the shade wanted.