Abstract
Silver compounds are employed for their antiseptic and germicidal action on bacteria. The effectiveness of such preparations is due largely to the free silver ions. The higher the concentration of free ions the greater will be the germicidal effect. New and Nonofficial Remedies (1937) states, “The antiseptic action of silver nitrate is complicated by irritation, pain, astringency, and corrosion. These may be desirable for the destruction of tissue or the stimulation of indolent wounds; but when they are not necessary for such purposes, they are distinctly undesirable. They may be avoided by the use of colloidal silver preparations.”
The colloidal preparations differ from the silver compounds in that the silver does not exist to any great extent in the form of free ions. The silver does not, therefore, precipitate chlorides or proteins and is noncorrosive and relatively nonastringent and nonirritating. The germicidal action is not proportional to the silver content of the preparations but is due to the liberation of very low concentrations of silver ions. The degree of ionization or liberation of silver ions varies with different preparations.
In an earlier paper 1 a new method was proposed for the evaluation of germicidal substances. The compounds were tested for their effect on the growth of living embryonic chick tissue as well as for their ability to kill bacteria. A number known as the toxicity-index was determined which is defined as the ratio of the highest dilution of disinfectant showing no growth of embryonic tissue in 10 minutes to the highest dilution required to kill the test organism in the same period of time. The tests were run at a temperature of 37°C in the presence of a standard amount of organic matter.
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