ETHYL alcohol remains the most popular of skin disinfectants and rightly so, because by and large it is the best. Inexpensive, readily obtainable, harmless to the skin and bacteriologically potent, its chief deficiency lies in its inability to kill spores—a deficiency shared by all the commonly used skin disinfectants. That its bactericidal power varies with the concentration of the solution used is well known, but what constitutes the most effective alcohol-water ratio has long been a moot question. The correct answer to that query, though a detail of surgical technic, is a matter of considerable practical importance.
According to traditional opinion (Epstein1) 50 per cent by volume is best. Harrington2 found, however, that 60 to 70 per cent by volume is the optimum concentration against dry test bacteria and that stronger concentrations are equally efficacious when the bacteria are wet. Beyer,3 who was first to point out