Abstract
The use of mercuric chloride as a disinfectant dates from the time of Robert Koch. 1 It has long been recognized as one of the most powerful disinfectants known. The germicidal power is exceedingly high in aqueous solution but enormously reduced in the presence of organic matter and some inorganic ions. It is precipitated by proteins and other organic compounds, hard water, alkalies, numerous salts, metals and sulfides.
It appears to be definitely established that mercuric chloride owes its germicidal properties to the positive or mercuric ion. This means that the compound is effective only in the dissociated state. Krönig and Paul 2 found that a 1–500 solution of the mercurial salt in water is much less than twice as active as a 1–1,000 dilution. The addition of any substance suppressing ionization causes a decrease in its germicidal efficiency. Sodium or ammonium chloride is sometimes added to increase the stability of the compound, but the germicidal power is greatly reduced due to a decrease in ionization. It is not applicable to the disinfection of sputum, excreta, and the like due to the formation of a coagulum which prevents further penetration.
In previous papers of this series 3 - 9 comparisons were made of the resistance of Staphylococcus aureus and embryonic chick heart tissue to phenol, Merthiolate, Metaphen, Mercurochrome, Hexylresorcinol, iodine, iodine tri-chloride and potassium mercuric iodide. Indices of toxicity were determined by dividing the highest dilution of the germicide that killed the tissue by the highest dilution of the chemical preventing growth of the test-organism. Theoretically the smaller the index the more nearly perfect the chemotherapeutic agent.
The methods employed were the same as those given in the first paper of this series.
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