Toluidine Blue is a dye that has certain rather unique properties, in particular, its spectral absorption characteristics, which do not resemble those of ordinary blue dyes (Fig. 1). While it has long been available on the market, its structure has never been divulged. It is not listed in Schultz (1) or the Colour Index (2), presumably because it is not important in the dyeing of textiles.1 In connection with other work on color and constitution being carried out in this laboratory, it became of interest to learn the structure of this dye.From the results of elementary analyses of the purified, salt-free dye, it was possible to write an empirical formula, C2 sH2 0N2Na2010S2. Qualitative reactions for classification indicated that it was an acid anthraquinone dye.

The condensation of methyl and ethyl α-phenyl-β-(para-substituted)benzoyl propionates with benzaldehyde and piperonal in the presence of sodium methylate, followed by acidification, has been found to produce cyclic compounds; the latter are shown to be lactols, six of which are described. The spontaneous ring closure is probably due to the highly branched chain. A mechanism for the reaction is proposed.On oxidation with chromic acid, α-diketones are formed; the latter contain the aryl group introduced as aldehyde. The lactols resemble triphenylcarbinol in several respects, forming a chloride, methyl ether, and acetate on appropriate treatment, all of which, on hydrolysis, regenerate the lactol. They also give colored solutions with concentrated sulphuric acid, from which the starting material is recovered on addition to water. From this work it is evident that in arylated γ-ketonic esters the hydrogen atom alpha to the ketone carbonyl group is more active in alkaline aldol condensations than the hydrogen in the alpha position to the carbalkoxy carbonyl group; the observation of others, that the conjugated system [Formula: see text] is more stable than [Formula: see text], has been confirmed.

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Aromatic sulfonic acids are readily identified in most schemes of qualitative organic analysis (1) by formation of the sulfonamide. A less familiar method is the production of salts between the acids and amines, or amine derivatives (2-11). Where applicable, this latter procedure gives results in a much shorter time. Neither of these means of identification is applicable to sulfonic acids when there is an amino group present.1 Inner salt formation prevents the use of the second procedure, and the sensitivity of the amino group to phosphorus pentachloride makes impossible the application of the first method.However, it has been found that when many aromatic sulfonic acids containing one amino group are diazotized and the NH2 replaced by Cl by means of the Sandmeyer reaction, the resulting chlorosulfonic acid is