At Last, A Disappearing Detergent

When rivers in the U.S. and Europe began to billow with evil-looking foam and tap water frothed like lager beer, the blame was quickly pinned on the synthetic detergents in modern cleaning agents. They wash shirts gleaming white and they make dishes shine, but the bacteria that swarm in soil and sewage do not eat them with the same appetite they have for old-fashioned soap. Rejected by the bugs, the detergents sweep through sewage plants and seep out of septic tanks into the ground water. They are not poisonous, but who likes creamy froth on his drinking or swimming water? Humans have no more taste for the stuff than the bugs do.

There is an obvious solution: cook up synthetic detergents that even choosy bacteria will consider delicious. And last week Esso Research and Engineering Co. of Linden, N.J., announced that it has finally found a recipe with the proper ingredients: pleasing to the bugs and cheap enough to fit the household budget. The concoction, however, was easier to dream up than to prepare.

The most popular detergent now in use, say Esso chemists, is TBS (tetra propylbenzene sulfonate). It forms the basis of just about every washday product on supermarket shelves-including Tide, Fab and Rinso Blue. Its complex molecule has many branches, and it contains a benzene ring of six closely bonded carbon atoms. This sort of thing is uncommon in nature, and bacteria find it unpalatable. So Esso chemists set out to make a molecule of a long, unbranched chain of carbon atoms, rather like a natural fat. That, they figured, would be something bacteria could get their teeth into, destroying it quickly. They tacked a sulfonic-acid group (-SO-OH)-the chemical that is responsible for the cleansing action-onto each long-chain hydrocarbon molecule. This is no easy trick to perform in a practical industrial process, but after years of work Esso chemists finally developed a novel way of making the reluctant chemicals react by jolting them with gamma rays.

When they passed the proper hydrocarbons, sulphur dioxide and oxygen near a chunk of fiercely radioactive cobalt 60, the gamma rays from the cobalt knocked a hydrogen atom off the hydrocarbon molecules, making them highly reactive. After enough of these free radicals had been formed, the cobalt 60 could be removed, and the reaction proceeded without further stimulation. The result was SAS (sodium alkane sulfonate), a long-chain detergent that washes clothes and dishes every bit as well as the troublesome TBS.

Next the Esso chemists dissolved their SAS in water and added bacteria from soil and sewage plants. The bugs went for the stuff like kids for peanut-butter sandwiches, gobbling most of it in a few days. Once their new detergent gets drained out of washing machines, say the ESSO men, it will not last long enough to make one horrid bubble.

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