F.C.G. Müller (same as Hubner and Post) made the barium salt of ortho brom toluene sulphonic acid, and then removed the bromine by treatment with sodium amalgam. The excess of alkali was removed by sulphuric acid, the sodium sulphate removed by evaporation and crystallization, and the residue dried. On treatment with phosphorus pentachloride an oily toluene sulphonchloride was obtained; this was decomposed by heating with water, the hydrochloric acid removed by repeated evaporations, and the syrup thus obtained evaporated to a crystalline condition. Several salts were made and studied. His amide melted at 90-91. Because this acid differed in properties from the two previously mentioned, Müller considered it to be the meta toluene sulphonic acid. About this time F. Gervor (Ann. chem. (Liebig) 169,383), made ortho diazo toluene sulphonic acid by subjecting ortho toluidine sulphonic acid to nitrous fumes. This was decomposed with alcohol under pressure, and a sodium salt of the acid obtained; this was converted into the chloride and an amide which melted at 148, differing in this and other properties from the amides of the ortho and para toluene sulphonic acids previously known. In 1874 Pechmann (Ibid., 173,195) obtained a quantity of para toluidine meta sulphonic acid by heating para toluidine with sulphuric acid, and crystallizing out the para toluidine ortho sulphonic acid and disulphonic acids, leaving the meta acid in solution because of its greater solubility. The diazo compound was made by treatment of the acid in alcoholic suspension with nitrous fumes, and decomposed with alcohol under pressure. Various salts of the resulting sulphonic acid were made and studied, also the chloride and amide which melted "somewhere below 100". In 1875 Pagel (Ann. chem. (Liebig) 176,297) working on ortho toluidine sulphonic acid, made a toluene sulphonic acid which resembled Muller’s. His amide melted at 104. In 1877 Beckurts (Ber.d.che. Ges. 10, 943), seeking for a good method of obtaining pure ortho toluene sulphonic acid, heated toluene and sulphuric acid in the ordinary way, and made the potassium salts of the resulting acids. By treatment with phosphorus pentachloride he obtained the acid chlorides which he separated by cooling to -15, and filtering off the solid para compound. The remaining liquid was transformed into an amide and purified by fractional crystallization. Two compounds were obtained with sharp melting points of 153 and 104. From this work he concluded that the sulphonation of toluene yielded all the three possible acids.