SACCHARIN, a name given to several totally different chemical substances of which the most noteworthy is the saccharin of commerce, a coal-tar product having an excessively sweet taste. This substance, which is the imide of ortho-sulphobenzoic acid and referred to scientifically as ortho-benzoicsulphinide, was discovered by Ira Remsen and C. Fahlberg in 1879 in the course of an investigation carried out at Johns Hopkins University, U.S.A., on the oxidation of o-toluenesulphonamide. The excessive sweetness of the substance was noticed accidentally by the latter observer who, after a day's work in the laboratory, washed his hands thoroughly and went home to supper, when he noticed that the bread tasted sweet, but closer examination showed that the taste came from his hands and even from his arms. He returned to the laboratory and tested the contents of each beaker and basin on the working bench until he came to the product possessing this remarkable property. This sweetening principle was the sub stance which subsequently attained world fame under its com mercial name of saccharin. It is still manufactured substantially in the manner worked out by Fahlberg. Toluene (q.v.) is sul phonated with fuming sulphuric acid to its ortho- and para sulphonic acids which are successively converted into calcium and sodium salts, and the latter treated with phosphorus penta chloride (or the trichloride plus chlorine). Phosphorus oxychloride is distilled off and the residue is thoroughly cooled and centri fuged to remove crystalline toluene-p-sulphonic chloride from the liquid toluene-o-sulphonic chloride, By a modi fication due to Heyden and to Monnet, this mixture of sulphonic chlorides is alternatively prepared by running toluene into excess of chlorosulphonic acid. The oily ortho-sulphonic chloride is converted by ammonium carbonate, or preferably by ammonia under pressure, into its amide, which on oxidation with alkaline permanganate yields the alkali salt of ortho-sulphaminobenzoic acid. This acid, when liberated from its salts by mineral acid is converted spon taneously into saccharin (formula I.) which is its internal anhy
dride.
Saccharin is a white crystalline substance subliming at ioo° and melting at 227-227.5° C. When pure and concentrated, it is 55o times as sweet as cane sugar, the commercial product being of 30o times the sweetness of sugar. It is only sparingly soluble in cold water, one part dissolving in 400 parts of boiling water. It is more soluble in alcohol, glycerol, ethyl acetate and acetone. From the last of these solvents it separates in large, colourless, transparent, monosymmetric crystals which when crushed or rubbed together display triboluminescence (W. J. Pope, 1895). The sweetness of saccharin is enhanced by mixing with dulcin, para-phenetolecarbamide, which itself has some sweetening property.
Saccharin forms a sodium salt (with 2H20) which dissolves readily in water and is known as soluble saccharin or crystallose.
The ammonium salt (formula II.), known as sucramine (melt ing point 15o° C), is obtained in white crystals equally soluble in hot or cold water; it is sweeter than saccharin, being 70o times as sweet as cane sugar.
Saccharin and its soluble derivatives are used as sweetening agents, and medicinally they are employed as sugar substitutes in diabetes, in liver disease and for the reduction of corpulence or wherever the use of sugar is undesirable. The physiological action is not, however, negligible, for saccharin decreases appetite, gastric secretion, peptic digestion and intestinal absorption.
In the United Kingdom there is an import duty of Is. 3d. per ounce on saccharin, and in the U.S.A. the import duty is $1.50+45% ad valorem per pound. Importation is prohibited in certain countries and in others high customs duties are imposed.
The lactones of saccharic acids (q.v.) are also known as "saccharins." By boiling dextrin or laevulose with milk of lime, a lactone of the formula CH2OH-CH.CH(OH).C(OH)-CH3 is obtained. It crystallises in prisms soluble in hot water and with bitter taste. Isosaccharin and metasaccharin, melting at 95° and 542° C, are formed by the action of lime on milk sugar. (See H. Pringsheim, Zucker-Chemie, Leipzig, 1925.)