When sulphur chloride is allowed to act upon phenolsulphonic acid whilst heat is applied, a yellowish-grey mass results, which dissolves in water, forming a reddish-yellow solution. Neutralised to acidity 10, it exhibits the following reactions:—
Gelatine————————Precipitate.
Ferric chloride————-Deep blue coloration.
Lead acetate——————White precipitate, insoluble HNO_3.
Aniline hydrochloride—-Precipitate.
Bromine water—————-No reaction.
The partly neutralised 2° Bé. solution of this product yielded a reddish-grey coloured leather, the qualities of which were very similar to that yielded by Neradol D.
3. Condensation with Phosphorus Compounds
Schiff's well-known synthesis, [Footnote: Liebig's Ann., 178, 173.] in which phosphorus oxychloride interacts with phenolsulphonic acid, yields a product which exhibits some tannin reactions, but which, when acting on pelt, converts the latter into a leather which, when dried, is very cracky. If, on the other hand, cresolsulphonic acid is condensed with phosphorus oxychloride by heating the two together, products eminently suitable for tanning purposes result. These products are non-crystalline bodies easily soluble in water, and are coloured bluish-violet by ferric chloride and precipitate gelatine. Solutions of the free acids and acidified solutions of the salts convert pelt into firm and white leathers possessing great softness and pliability.[Footnote: Austr. Pat, 66,895.]
4. Condensation with Aldehydes
By treating phenolsulphonic acid with acetaldehyde in the usual way, a viscous brown mass is obtained, which is very soluble in water, the solution being of a brown colour. When brought to acidity 10, the following reactions are exhibited by the product:—
Gelatine - - - Precipitate.
Ferric chloride - - Deep blue coloration.
Aqueous ammonia - - Cherry-red coloration.
Lead acetate - - - Yellowish precipitate, insoluble
HNO_3.
Aniline hydrochloride - - Yellow precipitate, soluble excess
aniline.
Bromine water- - - No reaction.
Tanning experiments with this substance yielded, even after extended tannage, an undertanned leather, the surfaces being coloured brown, the inner layers, however, white. Further neutralisation reduces the tanning intensity of the product; the addition of sodium sulphate to the original partly neutralised product hastened tannage, the leather, however, possessing dark colour and being undertanned. The following constitution may be ascribed to this product:—
OH OH
^ —-CH_2—-CH_2—- ^
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v v
HSO_3 HSO_3