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DYEING AND CALICO PRINTING.

5/4 Mordant.

625 grms. alum ; 450 grms. acetate of lead ; 2 litres boiling water.The following mixtures are in great repute with some dyers :—

A. B. C.

Alum.

16 kilos.

8‘o kilos.

10 kilos.

Acetate of lead

12 „

8-5 ..

10 „

Boiling water.

Extradt of Lima-wood, at

62 ,,

6o-o „

20 „

20° Baume.

2 „

30° Tw.

4*° (at 3°)

4 0 Tw.

In England it is customary to make up the mordants without the peach-wood liquor, and only add it when the colour is being prepared for printing.

Red Mordant (Liquor) for Garancin,

At 11° B. = 1-083 sp. gr. = 15° Tw.

25 kilos, alum ; xg kilos, of acetate of lead ; 80 litres of water.

Strong Mordant,

At ii° B.

2'5 kilos, alum ; 2 kilos, acetate of lead ; 63 litres of water.

Mordant for Red with Garancin.

Alum, i6'o8 kilos.; acetate of lead, I2'o8 ; water, 40'i6 litres.

According to the experiments of M. D. Koschlin, the mordant No. 2 (justmentioned) is strong enough to furnish, with nearly all tindtorial substances,the strongest tints which they can produce consistent with complete saturation.Instead of keeping one standard mordant, which, by being diluted with water,might serve to produce the different shades desired, the manufacturers preferto prepare a series of mordants graduated in strength according to the styleof work intended. The reason for this system is, that a strong mordant doesnot keep so well for any length of time ; moreover, since all these kinds ofmordants, even when kept in well-stoppered vessels, deposit in time more orless acetate of alumina, which is not readily again taken up in acetic acid, itis convenient not to prepare too much of any of these mordants at once.

Pure acetate of alumina in solution can be heated to the boiling-pointwithout decomposition, or without throwing down any basic salt, but themordants containing sulphate of potassa or basic alum become turbid onheating, and yield an abundant precipitate, which re-dissolves on cooling.According to Gay-Lussac this precipitate is hydrate of alumina; but sinceM. D. Koechlin found it to consist of 100 parts of sulphuric acid and 343'5 ofalumina, it should be considered as a mixture of alumina and a basic sulphateof alumina. It is an interesting fadt that the formation of this precipitatetakes place at a lower temperature, and more abundantly in the weaker mor-dants than in the stronger. The solution of subsulphate of alumina in aceticacid, obtained by partially precipitating at boiling heat a concentrated solutionof alum with caustic potassa or soda, yields a good mordant.

If it is needful to prepare a solution of acetate of alumina with sulphate ofalumina, the process is first to make a solution of the sulphate at from 31° to