These act by liberating oxygen, and in their action are themselves quickly destroyed. They are very inferior disinfectants, but are effective deodorizers. They readily and permanently destroy many colors, and are used as bleaching-agents.

1. Liquor hydrogenii dioxidi, peroxide of hydrogen, H2O2, is a watery liquid, rather unstable, and capable of yielding 10 volumes of free oxygen. The Pharmacopoeia states that it keeps better if a pledget of cotton is used to stopper the bottle instead of a cork. It destroys cork, rubber tissue, catgut, etc., and in contact with pus, blood, and other organic liquids splits into water and oxygen, giving off the oxygen so actively that it effervesces and produces a foam. In a cavity without free exit this gas may burrow into the tissues, with extension of the infection. It is a powerful deodorizer, and in dilution with not more than one or two volumes of water, is a valuable germicide. In the experiments of the Hygienic Laboratory (1912) cultures of typhoid bacilli were found sterile after an exposure of two and one-half minutes to 50 per cent. solution. (See also table of Post and Nicoll.) It is much employed as a gargle or mouth-wash, as in tonsillitis, diphtheria or pyorrhoea alveolaris, or for deeply furred tongue, and as a surgical cleanser in pus conditions. The author has employed it in the colon in intestinal putrefaction, to check the growth of anaerobic bacteria by liberating oxygen; but it proved too irritating to the bowel. It is also irritant in the throat.

2. Potassium permanganate, KMnO4, in aqueous solution, at once decomposes when it comes in contact with organic matter, giving up oxygen without effervescence and being reduced to the brown, insoluble potassium manganate. It is a chemic antidote to certain oxidizable poisons, such as morphine, phenol, and hydrocyanic acid, is a local irritant and stimulant, as in persistent sinuses, and in 1: 10,000 to 1: 1000 solution, is an antiseptic and deodorizer, as of foul ulcers and foul cancers. The crystals or the concentrated solution have been used with success locally in snake-bite. Von Adelung (1913) advises a 2 per cent. solution in ivy-poisoning. Death in a woman is reported from the corrosive effects of 2 1/2 drams (10 gm.) of the crystals swallowed with suicidal intent.

3. Sodium perborate, containing about 9 per cent. of available oxygen, is a white powder soluble in cold water. It is stable in cool and dry air, but in warm or moist air gives off its oxygen.