Science: Good Mixers

Synthetic wetting agents and detergents, newcomers to industrial chemistry, have just had the biggest year in their short but lively history. Their many manufacturers relaxed momentarily last week, beamed back upon 1941 when:

> Their U.S. production—which stood at zero as late as 1928—reached 100,000,000 lb. and was headed steeply upward into 1942.

> On their product was pinned 1942's surest badge of importance: military secrecy.

For chemists have found many uses for these useful chemicals which are best known to the public for their most useless ability: to scuttle a duck by altering water's surface tension and antipathy to oily feathers

Wetting agents now touch upon almost every aspect of life from obstetrics, where they are used as germicides, to undertaking, where they make embalming fluids more penetrating. Synthetic detergents—non-soaps with the cleansing properties of soaps—were first produced in the laboratory by the Frenchmen Dumas and Peligot in 1836. They began their concoctions with fatty alcohols extracted from whale oil, but the product was too costly to compete with that age-old detergent, soap. During World War I, when fats for soapmaking were scarce, German chemists again tried in earnest to concoct soapless soaps. Real success did not come until after the war, when they developed the sodium alkyl sulfates. Production of these substances was not practical until the 1930s, after techniques were developed which could convert fats to fatty alcohols under pressures of 10,000 to 15,000 lb. per sq. in.—100 times the pressures which were once tops in industry.

Today about 1,000 different wetting agents have been made in the U.S., are now marketed under some 270 bewildering trade names. Their chemical structure varies greatly and is quite complex. But all these compounds have one thing in common. One end of each long molecule is hydrophobic or water-hating, the other is hydrophilic or water-loving. Thus in a mixture of water and organic material such as oils, one end of the detergent molecule dissolves in the water layer, the other in the oil, breaking down the inter-surface tension or antipathy of the two substances.

Besides the aversion of liquid for liquid, wetting agents help break down the aversion (wherever it occurs) of liquid for solid, solid for solid, gas for liquid, gas for solid. So every place in industry where substances must mix, mingle and dissolve, wetting agents are being applied as fast as researchers learn how. They are used:

> In textile making, where they help dyes to penetrate fabrics quickly and evenly. Wetting agents also aid the moth-and flame-proofing of materials.

> In rubber making, where they help the dispersal of pigments and vulcanizing sulfur through latex.

> In metallurgy, where they are used to help 1) pickling—or acid-bath cleansing—of cast metals, 2) spreading soldering fluxes, 3) cleaning metal parts before electroplating, 4) wetting ore particles in flotation, etc.

^ In food industries, where they efficiently remove such poisonous sprays as arsenic from fruits and vegetables—and even help mix dough thoroughly for bakers.

> In mixing paints, enamels, printing inks, etc., and improving their spreading.