Drugs Used by the Dyer.

Posselt's Textile Journal 7, 1909

By A. Loeffler.
The drugs used by the Dyers are divided into three groups, viz.:
(1) Chemicals generally,
(2) Mordants,
( 3 ) Dyestuffs.

This division, based on the practical application of the materials in question, is not correct from a practical point of view.

Take for instance Chrome, which is generally called a mordant, but which acts as a dyestuff in the production of Chrome Yellow, again it might also be classed among chemicals, on account of it being used as an oxidizing agent, etc.

It is still more difficult to give theoretically a definition of the three groups.

Under chemicals will be understood, those materials which are employed in the preparing of the goods before dyeing, for instance, for bleaching, as well as such materials as are required during the processes of dyeing and finishing, without the coloring part of the color, either entirely or in part.

Mordants. This name is derived from the French name modre (to corrode) because the early French dyers believed that the utility of the metallic salts they employed consisted of their corrosive nature; it was believed that these substances opened the pores of the fibre, and thus rendered them more capable of absorbing the dyestuff.

At a late period it was recognized that the so-called mordants enter into a chemical combination with the dyestuffs and formed insoluble compounds or color lakes, hence the substances were considered principally as fixing agents for the dyestuff.

In many cases this is true; however there are dyestuffs which dye without the aid of a mordant but become faster to the washing and fulling by the application of the mordants. Again in some instances the mordant is an essential constituent of the colors, since without it no color at all, or only a worthless shade is produced. For instance Chrome colors (in general) and where minus Chrome only a worthless, or no shade at all would result.

We consider as mordants, substances which partly or wholly combine with the dyestuffs to form definite compounds in the fibre, thus distinguishing them from those chemicals which take part in the dyeing process without entering into the color.