No abstract

Wool which had previously combined with sulphuric acid or l-p-sulphophenylazo-2-naphthol combines with, and resolves, a reduced amount of mandelic or p-heptyloxymandelic acid. The results indicate that the anions of sulphuric acid and the arylazo-sulphonic acid also become attached to ammonium centres in wool, and that the numbers of sites on which the resolution of mandelate anions can occur is limited. A similar conclusion was reached from a study of m-nitromandelic acid and 5-(2 : 4-dinitroanilino)-2-ptoluidinobenzenesulphonic acid.

Immersed in aqueous (f)-mandelic acid at 31.3" 1 kg of wool absorbs 0.45 mole of the acid at pH 2.5. This value is closely similar to that reported for hydrochloric acid (0.4 mole). The mandelic acid is resolved into its optical antipodes by the wool, the (+)-forin being taken up more abundantly than the (-)-form. Mandelic acid is similarly resolved when it combines with L-arginine or L-lyshe to form salts. These facts, together with the knowledge that L-arginine and L-lysine are the principal basic amino-acids of wool, suggest that mandelic acid combines with wool to form a typical salt. A number of simple derivatives of mandelic acid are similarly resolved as also are certain related planar molecules of larger size and derivatives carrying long (C7-C10) alkyl chains. About 75 % of the mandelic acid bound at equilibrium combines within 4 min and resolution occurs from the beginning of the process. Dry-chlorinated wool and solventscoured wool behaved similarly. p-Decoxy-and p-hexadecoxy-mandelic acid were absorbed at a lower rate and the more complex acid was not resoIved at all. These acids and some of lower complexity, in contrast to mandelic acid, were retained by the wool after immersion in water. In this they showed in some degree the " affinity " characteristic of the acid dyes.