It may be prepared by the fusion of para-toluene sulphonic acid with potash; by the action of nitrous acid on para-toluidine; or by heating para-oxyphenyl acetic acid with lime.
It may be synthetically prepared by the fusion of cymol sulphonic acid with caustic potash; by the action of nitrous acid on 1-methyl-2-amino-4-propyl benzene; by prolonged heating of 5 parts of camphor with r part of iodine; or by heating carvol with glacial phosphoric acid.
With diazobenzene sulphonic acid in the presence of alkali and a trace of sodium amalgam, a reddish-violet coloration is formed on standing (E.
Reinsch on distilling catechin (the juice of Mimosa catechu); occurs free in kino and in beechwood tar; its sulphonic acid is present in the urine of the horse and man.
It may be prepared by fusion of ortho-toluene sulphonic acid with potash; by the action of phosphorus pentoxide on carvacrol; or by the action of zinc chloride on camphor.
Perkin; the method being to sulphonate anthraquinone, and then to convert the sulphonic acid into its sodium salt and fuse this with caustic soda.