sulphonated

Cresols, naphthalenes, and higher hydrocarbons are used as starting materials in the production of synthetic tannins; the former substances or their oxidation products are sulphonated by means of concentrated sulphuric acid, and the tanning matter produced by condensing the sulphonic acids with formaldehyde.

Synthetic Tannins Georg Grasser

The latter are formaldehyde-condensation products of sulphonated tar oils, or the hydroxylated derivatives of the latter.

Synthetic Tannins Georg Grasser

(CH_3) _2 is sulphonated, and the water-soluble sulphonation product heated with formaldehyde for some time, the product remains soluble in water and precipitates gelatine.

Synthetic Tannins Georg Grasser

Cresol is not so easily sulphonated as is phenol; _o_-cresol when heated eight to ten hours at 90° C. with one and one-half times its weight of concentrated sulphuric acid, yields _o_-cresol-_p_-sulphonic acid.

Synthetic Tannins Georg Grasser

When pyrogallol is sulphonated with concentrated sulphuric acid a violet-coloured sulphonic acid, soluble in water, is obtained, which, when treated with formaldehyde first in the cold and then when heated, yields a solid deep red-coloured mass, which precipitates gelatine but not aniline hydrochloride, and gives a blackish-brown colour with ferric chloride.

Synthetic Tannins Georg Grasser

Phthalic acid also is difficult to sulphonate: the sulphonated compound treated with formaldehyde gives only water-insoluble condensation products.

Synthetic Tannins Georg Grasser

Salicylic acid may, however, also be condensed with formaldehyde without first being sulphonated; in this case, a little hydrochloric acid should be present.

Synthetic Tannins Georg Grasser

A completely sulphonated compound should remain clear on dilution with water, or, in case precipitation occurs, the precipitate should be completely soluble in alkali or ammonia.

Synthetic Tannins Georg Grasser

CO. O.C_6H_5 is sulphonated, a product is obtained which is easily soluble in water, but which is identified as a mixture of the sulphonation products of salicylic acid and phenol, the salol being dissociated on sulphonation.

Synthetic Tannins Georg Grasser

QUINOLINE, when sulphonated and condensed with formaldehyde, yields a dark coloured condensation product, completely soluble in water; the solution does not precipitate gelatine.

Synthetic Tannins Georg Grasser