2g2

DYEING AND CALICO PRINTING.

various shades of purple or lilac ; mixed with red liquor it gives chocolates,of which more below.

Hyposulphite of iron can be used, according to M. Kopp’s experiments, asa mordant for tissues, but the low price of the acetate will prevent the use ofthe first-named salt from becoming general. Hyposulphite of protoxide ofiron, when exposed to the air, is slowly converted into protosulphate of iron,and lastly, into subsulphate of peroxide of iron, which is insoluble. Sincethis process of oxidation is very slow, the fixation of the peroxide, or sub-salt,upon the fibre is very intimate, and at the same time no perceptible weakeningof the tissues takes place. The hyposulphite is prepared either by the adtionof sulphurous acid on the protosulphuret of iron suspended in water, or bythe decomposition of the same sulphate by means of hyposulphite of lime, orby simply mixing hyposulphite of soda in crystals with a solution of sulphateof iron.

M. Persoz has proposed the use of an ammoniacal solution of pyrophosphateof iron. If this is printed on to the cloth, and slowly dried, it yields in thedye-beck, with madder, the most beautiful and pure purples and lilacs. Clothmordanted with this solution can even be dyed in madder becks of madderalready exhausted as far as other iron mordants are concerned.

Mordants for Browns and Chocolates.

These mordants are mixtures of those used for reds and for purples, and bysimply varying the proportions of these two liquors very many modificationsof tints may be produced. For simplicity’s sake we call the undermentionedpreparation for red (red liquor) Z in the after-mentioned compounds :—

Z.—Alum. io kilos.

Acetate of lead. io ,,

Water. 20 litres.

We designate as red mordant for brown the following mixture :—•

Alum.144 kilos.

Pyrolignite of lead. 144 „

Water.660 ,,

Crystals of soda (carbonate of) .. .. 4 „

With these the following brown mordants may be prepared :—

A. —Mordant Z .8 litres

Pyrolignite of iron at io° Baume (sp. gr. 1-075) .. 4 ,,

Extradt of quercitron at 20° Baume (sp. gr. 1-162) J litre

White starch .2'S kilos.

British gum.250 grms.

Gallipoli oil (huile tournante) .go „

B. —Mordant for brown . 12 litres 16 litres

Pyrolignite of iron at io° Baumd .. 2 ,, 4 „

Extrad of quercitron at 20° Baumd) ^ jj tre ^ jj tre

(sp. gr. 1-162).f

White starch . 3 kilos. 4 kilos.

British gum.375 grms. 500 grms.

Gallipoli oil (huile tournante) .. .. 125 ,, 125 ,,

We cannot in this chapter enter into the mechanical details of printing on themordants ; it may suffice to say here that it is done chiefly by means of rollers