Glauber's Salt and its Use in the Dyeing of Wools.

Practical Magazine 16, 1876

(Chemistry applied to the Arts, Manufactures, &c.
Dyeing, Calico Printing, Bleaching, Tanning, and Allied Subjects.)

The sulphate of soda (Na²6, SO³ +H²O) is known in commerce as Glauber's salt, and sold in large white crystals. Its remarkable chemical properties facilitate its use in the dyeing of wools. By its combination with acid the neutral sulphate is transformed into bi-sulphate, and this property is of great value in dyeing.

Ordinary litmus, violet litmus, fuchsine, red dyeing woods, turmeric, the red dyes, madder, logwood, and yellow wood are, it is well known, absorbed in only a very small proportion by woolly filaments in the presence of diluted acid; but if Glauber's salt is added to such a bath, then in consequence of the combination between this salt and the acid, a great part of the acid is precipitated, and all the advantage of the dyeing materials can be reaped.

Consequently the dyer has in his own hands the means of regulating the operation. It will be sufficient for him to add more or less Glauber's salt, but, of course, the quantity of it employed must be proportionate to the quantity of acid in the bath. If, as is sometimes the case, an attempt is made to attain the same object by rendering the bath stronger, or using it for a longer time, the harm done by entangling the fibres of the wool far outweighs the advantage gained by the use of the Glauber's salt.

With soluble indigo Glauber's salt gives an equally good result, but its action is diametrically opposite. It is well known how rapidly and unequally the bath of soluble indigo is exhausted. The rapid precipitation of this colouring substance is easy to understand, since in the presence of the acid the indigo possesses a great affinity for the woolly fibres. Hence one ought not to be surprised, after plunging three skeins into a bath of this nature, to see the third drawn out almost white. If Glauber's salt is added to the bath, it combines with part of the acid, and the operation of dyeing is rendered more uniform, while its duration is prolonged.

The following receipts for dyeing baths have been found useful:

Bluish green for three pieces of cloth.

Alum 5,040 kilogrammes.
Crystal 420 "
Soluble indigo or carmine 175 "
Glauber's salt 1,680 "
Flavin (Flawin) 0,0175 "

Billiard-table green for three pieces of cloth.

Alum 8,400 kilogrammes.
Glauber's salt 5,04O "
Carmine 1,680
Picric acid 0,350"
Heat to 167° F. for an hour and a half.

Logwood blue for four pieces of cloth.

Alum 4,480 kilogrammes.
Chromate of potass 1,120 "
Blue vitriol 0,560 "
Tartar 2,240 "
Glauber's salt 6,720 "
Sulphuric acid 2,24O "
Boil for an hour and a half, and add 22,400 kilogrammes of logwood.

- H. Söderstrom in Deutsche Wolfen Gezverbe.