of carbolic acid and then
completely filled with water, the water will absorb enough of the
carbolic acid to make a 5 per cent solution, and the water may be poured
on and off as long as the crystals remain. This 5 per cent solution is
the proper strength to receive sputum from tuberculous patients,
material ejected from the stomach in diphtheria, and fecal matter from
typhoid and cholera patients. This strong solution should not be used
on the living human body, since it is powerful enough to eat directly
into the flesh, and being a violent poison, it should be kept out of the
way of the household and carefully labeled to avoid accidents.

Carbolic acid has no value at all in the way of disinfecting the air,
although fifty years ago surgeons were accustomed to use a spray of
carbolic acid around the operating table before an operation in order to
destroy any germs of the air lingering in the vicinity. It is equally
futile to pour carbolic acid into sewers or to stand it around on the
mantelpiece for the purpose of disinfecting a room. Nor are sheets wet
in carbolic acid and hung over doorways and at the end of passages
anything more than a remnant of medievalism.

_Coal-tar products._

There are certain preparations made from coal-tar which, either alone or
combined with carbolic acid, have very strong disinfecting properties
and which are the bases of most of the patented disinfecting solutions
now sold. They are commonly called cresols or creosols and a 4 per cent
solution of any of the three ordinary forms will destroy bacteria in a
few hours. They are commonly used for receiving organic excretions of
sick persons in the same way as carbolic acid is used, and have about
three times the power of carbolic acid to destroy bacteria.

They have one great advantage besides the strength mentioned, in that
they are not materially affected or interfered with by the presence of
albuminous material. Carbolic acid in the presence of albuminous
material, like sputum, for instance, has the strength of the
disinfectant partly used up in combining with this albuminous material
so that the strength remaining for disinfection is weakened, and the
result is not as satisfactory as it would otherwise be. The coal-tar
products, on the other hand, are not so interfered with, and the
solution acts in full strength upon the bacteria.

_Mercury for disinfectant._

Corrosive sublimate, or bichloride of mercury, is one of the most activ