Sulphonic acids and their salts, obtained in the working up of waste acid arising in the refining of oils e.g. mineral, vegetable, or animal oils, or the distillation products of coal or bituminous slate by means of sulphuric acid by the following method, are used for decomposing fats and the like, and also as emulsifying agents. The waste is introduced into a sludge formed from alkaline-earth hydroxides or oxides to effect neutralization, and the solution of soluble sulphonates separated from the residue. The crude sulphonates obtained by evaporation may be purified by extracting them by means of an organic solvent e.g. alcohol. By treatment of the residue of insoluble sulphonates contaminated with asphaltic and resinous substances, with aqueous alkali carbonate, a solution of alkali sulphonates is obtained and a bye-product which may be used for neutralizing fresh waste acid, if it contains only small quantities of asphaltic substances, possibly after addition of alkaline-earth oxides, hydroxides, or carbonates. In examples, waste acids obtained in refining spindle oil (distillate), machine oil and a mixture of mineral oils are thus treated first with sludge of lime and then with sodium carbonate.ALSO:Sulphonic acids and their salts are obtained in the working up of waste acid which arises in the refining of oils, e.g., mineral, vegetable or animal oils, or the distillation products of coal or bituminous slate by means of suphuric acid. The waste is introduced into a sludge formed from alkaline earth hydroxides or oxides to effect neutralisation, and the solution of soluble sulphonates separated from the residue. The crude sulphonates obtained by evaporation may be purified by extracting them by means of an organic solvent e.g., alcohol. By treatment of the residue of insoluble sulphonates contaminated with asphaltic and resinous substances, with aqueous alkali carbonate, a solution of alkali sulphonates is obtained and a byeproduct which may be used for neutralizing fresh waste acid, if it contains only small quantities of asphaltic substances, possibly after addition of alkaline-earth oxides, hydroxides or carbonates, or secondly for the production of artificial asphalts, insulating materials and cements, if it contains large quantities of asphaltic substances. In examples, waste acids obtained in refining spindle oil (distillate), machine oil and a mixture of mineral oils are thus treated first with a sludge of lime and then with sodium carbonate. The alkali sulphonates may be decomposed by means of mineral acids, and the free sulphonic acids washed free from ash by dilute mineral acid. The products are stated to be wetting, emulsifying, foaming and fat-splitting agents. Specification 10321/93, [Class 2, Acids and salts, Organic &c.], is referred to.ALSO:Sulphonic acids and their salts, obtained in the working up of waste acid arising in the refining of oils e.g. mineral, vegetable, or animal oils, or the distillation products of coal or bituminous slate by means of sulphuric acid by the following method, are used as moistening agents for insoluble compounds. The waste is introduced into a sludge formed from alkaline-earth hydroxides or oxides to effect neutralization, and the solution of soluble sulphonates separated from the residue. The crude sulphonates obtained by evaporation may be purified by extracting them by means of an organic solvent e.g., alcohol. By treatment of the residue of insoluble sulphonates contaminated with asphaltic and resinous substances, with aqueous alkali carbonate, a solution of alkali sulphonates is obtained and a bye-product which may be used for neutralizing fresh waste acid, if it contains only small quantities of asphaltic substances, possibly after addition of alkaline-earth oxides, hydroxides or carbonates. In examples, waste acids obtained in refining spindle oil (distillate), machine oil and a mixture of mineral oils are thus treated first with sludge of lime and then with sodium carbonate.ALSO:The waste acid arising in the refining of oils e.g. mineral, vegetable, or animal oils, or the distillation products of coal or bituminous slate by means of sulphuric acid is introduced into a sludge formed from alkaline-earth hydroxides or oxides to effect neutralization, and the solution of soluble sulphonates separated from the residue. By treatment of the residue of insoluble sulphonates contaminated with asphaltic and resinous substances, with aqueous alkali carbonate, a solution of alkali sulphonates is obtained and a bye product which may be used for neutralizing fresh waste acid, if it contains only small quantities of asphaltic substances, possibly after addition of alkaline-earth oxides, hydroxides, or carbonates, or secondly for the production of artificial asphalts, insulating materials and cements, if it contains large quantities of asphaltic substances. In examples, waste acids obtained in refining spindle oil (distillate), machine oil and a mixture of mineral oils are thus treated first with sludge of lime and then with sodium carbonate.