2tb STERILIZATION, ANTISEPSIS AND DISINFECTION 
2. Silver *Sa/fe, — Silver nitrate is a much less efficient germicide 
than mercuric chloride, but it is quite extensively used upon mucous 
membranes. The soluble organic compounds of silver, as protargol, 
are less irritating than the inorganic salts and apparently nearly as 
efficient. 
Oxidizing Solutions. — 1. Potassium Permangajiate, KMn04.— Potas- 
sium permanganate is a strong disinfecting agent, but it is almost 
instantly reduced and rendered inert by organic substances. This 
greatly impairs its practical value. Nevertheless, it is used in surgi- 
cal asepsis and also in wells and cisterns which are to be freed from 
pathogenic bacteria. A strong solution is thrown into the well or cis- 
tern, enough to impart a very pronounced pink color to the water, 
and left for several hours. The water is fit for use when the last 
traces of color are removed by dilution or emptying and washing 
out the reservoir. This process is spoken of as "pinking" a well. 
2. Hydrogen Peroxide, H2O 2.— Hydrogen peroxide is a valuable 
germicide, applicable to the cleansing of mucous surfaces and wounds. 
It is readily reduced to H2O and nascent oxygen in contact with 
organic substances, and its efficiency is attributable to the latter 
element. It is essential that the peroxide actually reach the organ- 
ism to be destroyed in order to be effective. Usually hydrogen 
peroxide is quite acid in reaction and irritating for this reason. 
3. Chlorinated Lime or "5/eac/L" — Chlorinated lime is an excellent 
deodorant and germicide when it is fresh, but it soon loses chlorine 
when exposed to the air. Nascent chlorine is liberated from aqueous 
solutions, and reacts with water to form nascent oxygen and hydro- 
chloric acid, according to the equation 2C1 + HoO = 2HC1 + O. 
One part of nascent chlorine to 1,000,000 parts of water— a milligram 
to a liter in other w^ords— will kill moderate numbers of bacteria within 
a few minutes. For this reason, chlorinated lime is extensiA'ely used 
in the treatment of swimming pools to reduce the bacterial count. 
It is also used for the practical sterilization of urine, bath water, 
feces, and in the solid state, in privies, cellars and stables. 
Improvements in apparatus for dispensing chlorine gas have led to 
its use in preference to chlorinated lime. It is quite as efficient, less 
cumbersome to handle, and more constant in its action because the 
active substance — chlorine— is alone present. 
Phenols, Cresols.' — Phenol, popularly known as carbolic acid, and 
cresols, of which three are known— ortho, meta and para— are power- 
ful germicides: 
OH 
OH 
OH 
OH 
/^OH. 

r^ 
\/ 
\/CH3 
\/ 
cm 
Orfho cresol. 
Meta cresol. 
Para cresol. 
1 See Cooper: Biochem, Jour., 1911-1912, 6, 362; 1913, 7, 175, 187 for theory of 
disinfection by phenols, 
