Science: Deadly Soap

When bacteria are killed by carbolic acid or iodine, they stay dead; their tissues are destroyed by corrosive chemical action. But some modern soaps, though so bland that they are used for softening luxury fabrics, are a hundred times more toxic to bacteria than is carbolic acid.

No one knew why soaps had this deadly effect until Dr. E. I. Valko and Mr. A. S. DuBois of Onyx Oil & Chemical Co. of Jersey City explained it to the American Chemical Society this week. Actually the soaps do not kill bacteria, they permanently “narcotize” the germs. The bacteria show no signs of life, but by special efforts they can be “revived.”

The antiseptic soaps are not true soaps made of fat and lye but the recent “soapless soaps” (TIME, Jan. 5). The most powerful disinfectants among them are complicated organic compounds based on ammonium. Their use in softening, cleansing and disinfection is due to a positive charge on the organic part of the molecule. It is strongly attracted by protein, thus apparently seizes on the proteins of bacteria. By the only known test the bacteria are dead, i.e., they no longer increase and multiply bacteria.

Yet Dr. Valko and Mr. DuBois “revived” them: They used other soapless soaps, based on sulfuric acid, in which the active part of the molecule is negative. The positive and negative charges of the two soaps neutralized each other and the bacteria, thus freed of the soapy narcosis, went on with their life (i.e., propagated).

In ordinary washing this neutralization does not occur, and the narcosis amounts virtually to death. The very thin film of soap over each bacterium is thus far more effective in germicidal action than carbolic acid, which must consume the bacteria in order to kill them.