46 
PRINCIPLES OF BACTERIOLOGY 
Practical Disinfection for a brief description of Dakin’s 
solution. 
Iodine. —Tincture of iodine (7.5 per cent) has become 
in the last few years the standard disinfectant; in many 
hospitals it is the only agent used for disinfecting the 
held of the operation. It is most effective when freshly 
prepared; the parts on which it is to be applied should 
hrst be swabbed with alcohol and allowed to dry. 
Peroxide of Hydrogen. —As the presence of organic 
matter, such as pus, blood, etc., distinctly diminishes its 
effects, one should always remove these from wounds 
before applying the peroxide; it acts upon bacteria by 
liberating oxygen. 
Permanganate of Potassium. —Permanganate of 
potassium acts, as does the peroxide of hydrogen, and 
is a powerful germicide. 
Bichloride of Mercury (Mercuric Chloride.) —Bichlor¬ 
ide of mercury is a powerful germicide; a solution of 
1:1000 is commonly used; this will kill the vegetative 
forms in a few minutes, and in solution of 1:500 will 
kill spores in a few hours. The addition of 25 per cent 
alcohol greatly increases the germicidal action of bi¬ 
chloride of mercury. There are certain disadvantages: 
it is apt to cause local necrosis (destruction) of tissues 
because of its great affinity for proteins, or injure the 
kidneys by absorption; it is unreliable for disinfection 
of feces, sputum, etc., and can not be used for steriliza¬ 
tion of instruments. It is used almost exclusively for 
irrigating wounds and disinfecting the skin. 
Silver. —Silver preparations such as silver nitrate (0.1 
to 4 per cent), argyrol, protargol, etc., are used prin¬ 
cipally upon mucous membranes and in the eye (e. g., 
in the newborn babies to prevent the ophthalmia of the 
newborn). 
