When toluene is treated with chlorsulphonic acid there are formed besides the ortho- and para- chlorides also ortho and para sulphonic acids. These of course are in solution in the water from which the chlorides separated. In order to recover the ortho-acid, the solution was neutralized with chalk forming the calcium salt: this converted into the potassium salt which by evaporating the solution to dryness was obtained as a white crystalline powder. When treated with PCl5 in the manner already described this gave a mixture of ortho and para sulphonchlorides consisting of about ⅓ ortho and ⅔ para.

Formation of Orthosulphobenzoic acid from Sulphinide.

Benzoic sulphinide may be converted into a sulpho-benzoic acid (1) by boiling with Ba(OH)2, (2) by heating in a closed tube with conc. HCl or (3) by evaporating on the water bath with HCl.

1. Three gramms of sulphinide were boiled in a flask connected with an inverted condenser for about two days with an excess of Ba(OH)2. There was formed in the flask a hard mineral-like mass which was insoluble in water and cold diluted HCl but dissolved in hot HCl with effervesence. This was a Barium salt, probably basic (?) of ortho sulphobenzoic acid. There was also formed an easily soluble barium salt of that acid. The former was dissolved in H2SO4 and treated with BaCO3; the filtrate from the BaSO4 which contained a soluble barium salt was added to that above mentioned and the barium exactly precipitated with H2SO4 and the filtrate evaporated to dryness giving the free acid but not in a perfectly pure condition.

2. 2.75 gr. of sulphinide was sealed up in a tube with pure conc. HCl and heated two hours to 150°. On cooling nothing separated; the liquid was evaporated to dryness giving 3.2 gr of acid and ammonium chloride. The reaction taking place here may be represented thus:

CO COOH
╱ ╲ ╱
C6H4 NH + 2H2O + HCl = C6H4 + NH4Cl.
╲ ╱ ╲
SO2 SO2OH

3. A more convenient method for obtaining the acid than either of the above, is to heat the sulphinide with conc. HCl on the water bath for two days. Then evaporate to dryness and dissolve the residue in a small quantity of water. If the sulphinide contained any para-sulphamide, as is usually the case, this will be left undissolved and most of the NH4Cl will crystallize on standing. This solution by slow evaporation deposits large colorless crystals of the free acid.

This acid is soluble in about two parts of cold water, very difficultly soluble in absolute alcohol and almost completely insoluble in ether. It does not melt under 250° but considerably above that it melts, at first apparently without change and then with slight sublimation of a very deliquescent substance, probably the anhydride.

Two determinations of the S. made by Mr. A. F. Linn, gave the following results.

I ·1358 gr substance gave ·1855 gr BaSO4 representing 15·72% S.
II ”” ”””